     [file version.texi not included]

Gri
***

Gri is an extensible plotting language designed for scientists.  It can draw x-y plots, contour plots, and image plots, and has rudimentary programming capabilities.  It is not mouse driven, nor gui-based; rather, it is an interpreted scriping language.  Users regard it as an analogue to the latex document formatting language: users gain considerable power, at the price of a moderate learning curve.

This manual describes Gri version 2.12.23 (c) 1991-2011, Dan Kelley

Gri is released with the GNU Public License (License).

Introduction
************

Gri is a programming language for drawing science-style graphs. It is not mouse-driven, and it does not draw business-style graphs (e.g. pie charts, three-dimensional graphs).  Gri has substantial power in advanced applications.  It has been proven to be easy to learn; for simple applications, the learning curve is less than an hour.  Many users regard Gri as the plotting equivalent of the LaTeX document preparation system.

Computers Gri works on: unix computers of many types, plus Microsoft Windows, and Macintosh OSX.  You'll find Gri pre-packaged for various unixes, e.g. linux/debian, linux/redhat, and freeBSD.

Capabilities of Gri are those scientists commonly want, since Gri was written by a scientist.  It is not so useful for business people -- e.g., Gri draws xy graphs (X-y Plots), contour plots (Contour Plots), and image plots (Images), but it will not draw pie-charts unless you teach it how.  The list of capabilities of Gri is similar to many packages, but unlike many of the other packages, Gri gives you control over line widths, fonts, grayscales, etc.  (Getting More Control), and it is a programming language of moderate power.

The Gri drawing metaphor is that of pen on paper.  The ink in the pen is opaque.  An item drawn in white ink will erase a previously drawn underlying object drawn in black ink.  For example, to draw a timeseries curve in which the region between positive data values and the y=0 axis is filled with black ink, you might use (draw curve filled) to draw the timeseries with black ink (the default color), blackening the area between the curve and the lower axis.  Then you could load white ink into the pen (using the set graylevel 1 or set graylevel white command) and white-out a box drawn between the zero line and the lower axis.  Then you'd load black ink back into the pen (set graylevel 0) and draw the curve again, so that the negative part would appear again.

Input/output in Gri may be interactive or non-interactive.  For interactive use, type gri at the system commandline prompt.  For non-interactive use, with Gri commands in a command-file called cmd.gri, type gri cmd.gri.

Gri output is in the PostScript page description language.  The output is therefore of high quality, device-independent, capable of being inserted into popular text processors (e.g. LaTeX), and easily displayed.

Online help: the Gri command help makes Gri list the first words of all known commands, along with a hint for getting further help.  To get more information, type help followed by a command-name (e.g. help read).  There is also a tiny bit of information stored online and categorized by topic.  Get this by typing for example help - strings (Online Help).

Data analysis in Gri is limited.  It has rudimentary data analysis functions, such as regression, column manipulation, smoothing, etc, but it is not intended as an integrated analysis/graphics package.

System calls are an easy and important facet of Gri.  It is easy to use operating system commands within Gri (System; Operating System; Get Env).  This allows you to use familiar, powerful tools, and keeps Gri simple. Particularly useful is the ability to read files through operating system filters (Open).

Programming Gri is quite straightforward, and users familiar with other programming languages find it easy.  If Gri lacks a drawing method, you can add it fairly easily, since Gri has programming elements such as if statements (If Statements), while loops (While), facilities for interacting with the user (Query), and mechanisms for storing numbers in "variables" (Variables), and text strings in "synonyms" (Synonyms).  The Gri syntax can be augmented easily (Adding New Commands), and these augmentations can be stored in a startup file (Resource File), creating personalized versions of Gri.

Manuals: Gri has an online texinfo manual, a PostScript manual, a WWW manual, a cookbook and several reference cards.  It also has several discussion groups (Discussion Group).

Version Numbering Scheme

When you launch Gri interactively (without naming a commandfile, i.e. by just typing gri at the unix prompt), you'll see something like

      gri - scientific graphic program (version 2.12.23)
      GPL Copyright 2008 by Dan E. Kelley.

      Type `help' for an overview of Gri commands, or see the
      full manual at
          /usr/share/doc/gri-2.12.23/html/index.html
      and its text-only version in the 'gri' INFO node.

      Visit http://gri.sourceforge.net for updates and resources.
     gri:

The last line is a prompt, suggesting that you type in Gri commands. You may type quit to get out of gri.

The first line gives the version number.  You can also get this by running Gri with the command gri -v.  Version numbers have three numbers separated by periods.  The first number increments for major changes, the second for smaller changes, the third for still smaller changes.  The second number also indicates whether a copy is an experimental version or a more reliable release version.  Experimental versions have the second digit being an odd integer, while release versions have this digit being even.

Simple Gri Program and How to Run it
************************************

This chapter introduces Gri with a common example: an x-y graph.  The example is discussed in detail later (X-y Plots).  The data files and command files here and throughout the manual should be available to you in a directory .../gri/examples on unix machines.

Gri Command file
================

Here is a Gri command file to plot a linegraph of a set of (x,y) data, stored as space-separated columns in a file called example1.dat:

     # Example 1 -- Linegraph of data in separate file
     open example1.dat     # Open the data file
     read columns x y      # Read (x,y) columns
     draw curve            # Draw data curve
     draw title "Example 1"# Title above plot

The first line is a comment, as are all things following hash symbols (#). (An exception to this rule is made within strings contained within the double-quote character ".  This allows sed system commands to work as expected; (System).)

The other lines are Gri command lines; (X-y Plots) for more explanation.

Data File
=========

The data file example1.dat looks like:

     0.05 12.5  # first point
     0.25 19    # second point
     0.5  15    # third point
     0.75 15    # ... you get the idea!
     0.95 13

Note that spaces (or tabs) separate numbers.  Any data line may have a comment on it, just as any command line may.

Running The Command File
========================

Type gri example1.gri at the system prompt.  Gri will create a PostScript file called example1.ps.  For details on running Gri see Invoking Gri.

Output Graph
============

The output PostScript file is called example1.ps.

To view Gri output, use your favorite PostScript previewer.

Note that in the above example, Gri automatically chose reasonable scales for the axes, based on the range of the data.  The next chapter illustrates that Gri also gives you control over such things.

Invoking Gri
************

Invoking Gri in a nutshell
==========================

First, the short story.  In 90 percent of cases, Gri is run as

     gri myscript

where the file myscript.gri holds a script (list of Gri commands), and Gri will create a PostScript file called myscript.ps with the output.

Some folks like to give the .gri suffix explicitly, so they would invoke Gri as

     gri myscript.gri

instead.

If you'd rather not have myscript.ps as the PostScript output file name (let's say you prefer graph1.ps) you'd do

     gri -output graph1.ps myscript.gri

Few readers will need to know more than this.  But, for the rest, the table in the next section gives full details on all the optional arguments that Gri can handle.

Using Gri to draw things
========================

To draw things, invoke Gri as

     gri [OPTIONS] [CmdFile [optional_arguments]]

where the square brackets indicate that the enclosed items are optional.  The OPTIONS item may consist of one or more of the following (explained below):

     [-batch]
     [-b]
     [-chatty N]
     [-c      N]
     [-debug]
     [-d]
     [-directory_default]
     [-directory pathname]
     [-help]
     [-h]
     [-no_bounding_box]
     [-no_cmd_in_ps]
     [-no_startup_message]
     [-output PS_file_name|SVG_file_name]
     [-private]
     [-no_private]
     [-publication]
     [-p]
     [-superuser N]
     [-trace]
     [-t]
     [-yes]
     [-y]
     [-version]
     [-v]
     [-warn_offpage]
     [-no_warn_offpage]

Here, the optional optional_arguments are a mechanism to customize the action of the given Gri script from the commandline. After Gri processes standard arguments (e.g. -t for tracing), it puts the remaining commandline arguments into a list.  This behavior is borrowed from C and othe languages, so Gri borrows the name of the list as well: it's called the "arg" list, and its elements are available with the RPN operators named argc (Solitary Operators) and argv (Unary Operators).

For a note on usage within the Emacs gri-mode, see Filename arguments when running gri.

Details of command-line options

  * -batch or -b Stops Gri from printing out prompts and hints.

  * -chatty N or -c N Make Gri print out various informative messages.  The numerical value gives a level of chattiness.  A value of 1, the default if the -chatty code is not supplied, tells Gri to keep you informed of some important things, like the success in gridding data for contouring.  Higher values make Gri tell you more:

     Information printed at various chatty levels:

       * 0 The bare minimum is printed.  Thus invoking Gri as gri -c 0... will make it as quiet as can be.

       * 1 or higher (the default) The full filenames of the commandfiles are displayed at startup time.

          convert columns to grid prints percentage of grid filled, as well as a suite of diagnostics, if you've let it calculate the region of influence automatically.  It also prints a warning of the time it expects to take, before starting the calculation.

          convert grid to image prints characteristics of image created, including amount of image clipped.

          read grid data reports number of data values it could not read (since they were nonnumeric).

          draw symbol reports number of data points not drawn because they were missing or outside clip region (if one exists).

       * 2 or higher draw contour prints value of contour being drawn.

          open "...|" prints the command to be passed to the operating system as well as the name of the temporary file being created; also notifies user when the temporary file is destroyed.

          show image reports histograms in intensity bands of 8 units, instead of the default 16 units.

       * 3 or higher show image reports histograms in intensity bands of 4 units, instead of the default 16 units.

  * -debug or -d Sets the built-in variable flag ..debug.. that you can use to isolate blocks of code.

  * -directory_default Reports directory where gri.cmd is expected to be found, either in the default location or the one specified by -directory commandline option.

  * -directory pathname Specifies the directory where Gri looks for the startup file gri.cmd.  (This file teaches Gri the standard commands; Gri will report an error and die if it cannot find this file.)  If this switch is not provided -- and it is normally not -- then Gri looks for gri.cmd in a standard system directory (sometimes, but not always, /usr/local/share/gri/2.12.23) which was specified during the compilation of the Gri program itself.  For more on how Gri looks for gri.cmd, see the subsection below.

  * -no_bounding_box Make the so-called ``bounding box'' in the PostScript file be the full page.  The bounding box is used by some PostScript previewers to clip the image to just the drawn parts of the page, and is used by the epsfbox macro in latex to automatically determine the geometry of the graph for inclusion in text.  Normally the bounding box is calculated automatically, to enclose all the items drawn on the page. But the box may also be set with the set bounding box command (Set Bounding Box).

  * -no_cmd_in_ps Prevent Gri from inserting the lines of the commandfile into the PostScript file as comments.  (These comments can be used by the -creator commandline option (see above), but they take up a little bit of space and users might sometimes want to get rid of them.)

  * -no_warn_offpage Do not warn if items are offpage.  (Contrast this with -warn_offpage.)

  * -output PS_file_name Specify the PostScript filename.  If this is not specified, the PostScript filename is derived from the name of the commandfile (e.g. mygraph.gri produces mygraph.ps), or, for interactive use, it will have a name like gri-00.ps, or gri-01.ps if the former file exists, etc.

  * -output SVG_file_name Specify the SVG filename.  This is a pre-feature, as of version 2.12.x, meaning that SVG output is not working properly yet.  If you specify an SVG file name, you will see a long list of warnings.  These are debugging messages, and are not specific to your actual Gri script.  For example, you will see warnings about centring strings, even if you are not centering any strings.  This manual does not contain a list of working features (or broken features) for SVG output; the idea is that a discussion of such things be done using the bug-reporting system of the Gri website Reporting Bugs.  In addition to bugs, the author is interested in users' opinions on the scheme of the SVG, especially the hieararchy of groupings of graphical elements.  It is because such things are being altered that this is designated a pre-feature.

  * -no_startup_message Stops Gri from printing the startup message.

  * -private Prevents inserting any information about the user into the PostScript file (see -no_private, next).  As of version 2.12.10, this privacy option is assumed by default.

  * -no_private Instructs Gri to include comments in the PostScript file that identify the user, state the commandline arguments used in invoking Gri, and that list all the commands that were executed.  This information can be recovered by calling Gri on the PostScript file, with the -creator commandline argument.  Until version 2.12.10, the default was to include this information, but a change was made out of privacy concerns.

  * -publication or -p Sets the built-in variable ..publication.. to 1.  You may use this to distinguish between working plots and publication plots, as in this example:

          if !..publication..
            draw time stamp
            draw title "working version of plot"
          end if

  * -superuser (This option is included here only for completeness.  It should only be used by developers (who will alter the code to print debugging information if -superuser is set in addition to -debug). An optional value can be inserted (e.g. -superuser 2) to set the debugging level (retrievable by the function superuser()) to indicated integer value.  Specifying the -superuser command-line option sets the built-in variable ..superuser.. to 1 or the specified value.)

     For flag meanings, see superuser command (Superuser). Using the question-mark symbol ? instead of a flag number makes Gri print out the list of flags.

  * -trace or -t Makes Gri print out command lines as they are executed; this has the same effect as the set trace command.

  * -version or -v Display version information and exit successfully.

  * -warn_offpage Causes warnings to be issued for all items drawn far off a 8.5x11 inch page.  This is the default.  (Contrast with -no_warn_offpage.)

  * -yes or -y Bypasses all query commands, making Gri act as though the user typed a carriage-return (thus giving the default) for each query.

  * -help or -h Prints explanation of options.

  * CommandFile If a command file CommandFile is specified, then commands will be read from that file instead of the keyboard.  If the chatty level is 1 or larger, Gri prints the names of the commandfiles at startup time.  It is conventional but not necessary that the filename ends in .gri.  If the filename does end in .gri, you may delete this suffix; Gri will assume it as implied.

Executable scripts. If you don't need to supply commandline options, you can put the following line as the first line in your Gri program

     #!/usr/bin/gri

(or point to wherever Gri is located on your machine), and chmod +x the file.  Then you can run Gri simply by naming the file.  There is no particular advantage in this, except for saving the typing of a few characters, but some folks like this.

How Gri locates the gri.cmd file. In a normal installation, Gri finds the gri.cmd file all by itself.  However, developers and some others may wish to control where Gri looks for this file.  The rules below specify how Gri looks for gri.cmd.

Case 1
     If -directory was given on the commandline used to invoke Gri (e.g. gri -directory /some/place mycommand_file.gri), then Gri will use the gri.cmd in the named directory.  An error will result if gri.cmd is not found there.

Case 2
     If -directory was not given on the commandline, then Gri looks for gri.cmd in a location that was specified during compilation.  If gri.cmd is found there, then it is used.  If it is not found, then Gri checks to see if an environment variable named GRI_DIRECTORY_LIBRARY is defined.  If so, then Gri takes this to be the name of a directory that contains the gri.cmd file.  If gri.cmd is not found there, an error results.

Extracting commandfile from a PostScript file
=============================================

     gri -creator PostScriptFile

See also -no_cmd_in_ps.

The -creator flag makes gri examine the indicate PostScript file, and produce a facsimile of the command file (or interactively-typed commands) that created this PostScript file.  (This only works if the Gri command that created the PostScript file used the -no_private commandline argument.)

Controlling Axes, Fonts, Colors, etc
************************************

Gri provides a great many things that you can control, if you want to. An introduction to some of these things is presented in the sections below.

An example
==========

Below is a followup to the previous example, which names the x and the y axes.

     # Fancier version of Example 1
     open example1.dat
     read columns x y
     set x name "Time, hours"
     set y name "U, m/s"
     draw curve

The difference is that the x and y axes are named with a set command.  There are many set commands, and they are all pretty simple, e.g. set x size 15 makes the x-axis be 15 centimeters long, instead of the default of 10 centimeters.  Indeed, you can control anything you want in gri, e.g. graph size, line width, fonts, etc etc. Speaking of fonts, the $\alpha$ type of latex formatting of Greek letters is supported in a limited way. Also, Gri handles ISO-Latin-1 encodings as well as the U.S. style.

The example below illustrates a few more set commands.  This example is intentionally complicated, being about a good example of the level of complexity of many plots made by Gri.  Read the comments to see what is being done, and consult the plot as you read the commandfile.

     # Example 3 -- Controlling scales, etc
     #
     # Example of how to control axis scales, etc.  This example makes
     # two panels, plotting the same data in different ways.
     #
     #
     # ----- PANEL 1 ------------------------------------------------
     #
     # Set up the x axis.
     #
     # Make the x axis run from 0 to 1, with labelled tics each 0.25.
     set x axis 0   1   .25
     # Make the x-axis be 5 cm long; in other words, make the plot 5 cm wide.
     set x size 5
     # Put 2 cm of space between the left edge of the plot and the left
     # edge of the paper.
     set x margin 2
     # Give the x-axis the name "t" with subscript 0.
     set x name "$t_0$"
     #
     # Set up the y axis.
     #
     # Make the y axis run from 10 to 20, with labelled tics at intervals
     # of 5 and smaller, unlabelled tics, at intervals of 1.  Other
     # commands are similar to those for the x-axis.
     set y axis 10 20 5 1
     set y size 10
     set y margin 2
     set y name "F"
     #
     # Now, read our simple data set.
     open example1.dat
     read columns x y
     close
     #
     # Draw a curve connecting these (x,y) data.  Note that the axes, as
     # defined above, will be drawn automatically along with the curve.
     draw curve

     #
     # ----- PANEL 2 ------------------------------------------------
     #
     # OK, now for a more complicated version.  We'll keep the same data, but
     # redraw it in a new panel, to the right of the first graph.  So, the
     # first step is to increase the x margin.  The {rpn} command simply
     # creates a number which is the sum of the old x margin (stored in
     # the variable ..xmargin..) and the old plot width (stored in
     # the variable ..xsize..), plus an extra 1 cm
     set x margin {rpn ..xsize.. ..xmargin.. + 1 +}
     #
     # Set the line thickness for the curve to 1 point (0.3 mm) and the
     # axis line thickness to 0.2 points (0.1 mm).
     set line width 1.0              # points
     set line width axis 0.2         # points
     # Set the tics to be 1.5 mm.
     set tic size 0.15               # centimetres
     # Draw axes and frame, with axes offset from frame.  Some
     # people find this more attractive.
     set axes style offset
     draw axes 1
     # Now draw the actual curve.
     draw curve
     # Superimpose dots (diameter 1.5 mm) at the data.
     set symbol size 0.15
     draw symbol bullet
     #
     # All done.
     # Draw a title above the plot.
     set font size 20
     \label = "Example 3 -- scales, axes, etc"
     draw label "\label" at          \
         {rpn 8.5 2.54 * "\label" width - 2 /} \
         {rpn ..ytop.. yusertocm 2 +}\
         cm

Axis scaling
============

Gri normally assumes that you are plotting scientific graphs, and therefore whenever it sees a command like draw curve or draw symbol, it draws an appropriate axis first.  You can turn this feature off, by using draw axes none before the other draw command.

Furthermore, Gri picks axis scales by itself, by scanning the (x, y) columns.  If you don't like the scales Gri picks, you can override them (Range).

Gri normally draws axes labelled at left and bottom, and with an axis frame with tics all around.  If you don't like this default axis style you can specify other styles.  For example, if the commands draw x axis and draw y axis are placed before the draw curve command, Gri will realize you've already specified axes, and just draw them on the left and bottom sides of the box, without completing the axis frame.

For your general use, Gri stores the minimum and maximum x and y values of the axes in the variables ..xleft.., ..xright.., ..ybottom.., and ..ytop...  It also stores the increments used in labelling these axes in the ..xinc..  and ..yinc.. variables.

To determine the minimum and maximum values of column data, you may use the built-in RPN functions min, max, and mean (Manipulation of Columns etc).

Gri stores the last (x,y) pair on a curve (whether data or axis) in the ..xlast.. and ..ylast.. variables

Gri stores the axis sizes in ..xsize.. and ..ysize...  It stores the space to the left of the plot in ..xmargin.. and the space below the plot in ..ymargin...

Logarithmic and linear axes
===========================

Axes are linear by default; to make logarithmic axes, use commands set x type log and set y type log.

Axis Length
===========

The axes are normally 10 centimetres long.  To set the axis lengths (in centimetres), use commands like set x size 5 and set y size 7.  Some people like the ratio of axes to be in the so-called golden ratio (root(5)-1)/2; to get that, you could do this:

     set x size 15
     set y size {rpn ..xsize.. 5 0.5 power 1 - 2 / *}

For maps, you'll want the plot scaled so that shapes retain their aspect ratio.  To do this, do set x size .cm. and then do resize y for maps (or vice versa).

Axis Range
==========

To override axis ranges set by Gri, use set x axis and set y axis.  With these commands, you specify the range of the axes; you may also set the interval for numbered tics, and an interval for unnumbered tics.  The unnumbered tics must be at an interval that divides evenly into the numbered tic interval, but the numbered tic interval need not divide into the min/max range.  Thus, set x axis 0 1.1 0.5 will create an axis that will range from 0 to 1.1, with labelled tics at the values 0, 0.5 and 1.

Axis Name
=========

To set the name of the x axis, use set x name "string", and similarly for the y-axis.  The default names are x and y.

Axis location
=============

If you don't like the default position of axes (at left and bottom), you may get Gri to draw axes anywhere you like, using commands like draw y axis at right (so the y axis is at the right-hand end of the x range) or draw x axis at top (so the x axis is at the top of the plot); you may even specify an exact location, such as draw x axis at 22.2.

Normally, the x axis is placed at the bottom end of the y axis, and the y axis is placed at the left end of the x axis.  Some people prefer a style in which the axes are positioned a small offset away from these locations.  To get this effect, you may either position the axes yourself, or simply use the set axes style offset command (Set).  If you want this axis style for all their plots, put the line set axes style offset in your ~/.grirc startup file (Resource File).

Fonts
=====

Fonts are selected with set font to (Set Font To) and font sizes are selected with set font size (Set Font Size).

Much more about text, including how to draw mathematical symbols, how to use subscripts and superscipts, how to write non-English (accented) European text, etc, is discussed (Text).

Colour of ink in pen
====================

The darkness of the ``pen'' used in drawing commands (for either lines or for text) is set by set graylevel .brightness..  A brightness value of 0 corresponds to black ink, and a brightness value of 1 corresponds to white ink.  Values outside this range are clipped to the nearer endpoint.  Values inside this range choose a proportional graylevel in between; for example, set graylevel 0.5 gives a 50 percent gray tone.

The graylevel applies to text as well as lines.  Often you'll want to draw a gray line and a black label beside it, or you'll want to set a graylevel temporarily.  Here's how to do it:

     # Save old graylevl, set, then reset to old
     .old_gray. = ..graylevel..
     set graylevel 0.5
     draw curve
     set graylevel 0
     draw label for last curve "TEST"
     set graylevel .old_gray.

The color of the "pen" may be set to any value you can describe with an RGB (red, green, blue) or HSB (hue, saturation, brightness) specification, or a color name.  This pen color applies to everything, even text.

The set color \name command

Set the pen color to the indicated name.  There are two types of names: hexadecimal-triplet names and English names.

Hexadecimal-triplet names are of a form often used in web-pages.  They consist of exactly 6 characters, which are divided by Gri into three sets of two characters, specifying the red component, the green component, and the blue component of the color, respectively.  These components are in hexadecimal notation, i.e. ranging from 00 to FF, indicating values from 0 to 255.  For example,

     set color ACD4EF

sets a pastel blue color, almost the color of a robin's egg.

The English colors are written simply in the form

     set color blue

where the color is from the following list.  (Gri requires that you use the exact form shown, including the capitilization.)  The color mixes are identical to those used in X11.

     NAME               RED    GREEN  BLUE
     "white"            1.000  1.000  1.000
     "LightGray"        0.827  0.827  0.827
     "darkslategray"    0.184  0.310  0.310
     "black"            0.000  0.000  0.000
     "red"              1.000  0.000  0.000
     "brown"            0.647  0.165  0.165
     "tan"              0.824  0.706  0.549
     "orange"           1.000  0.647  0.000
     "yellow"           1.000  1.000  0.000
     "green"            0.000  1.000  0.000
     "ForestGreen"      0.133  0.545  0.133
     "cyan"             0.000  1.000  1.000
     "blue"             0.000  0.000  1.000
     "skyblue"          0.529  0.808  0.922
     "magenta"          1.000  0.000  1.000

To get more colors than those provided in the above list, use the read colornames command.

You should do a test case for your printer to see which colors you find most to your liking.  You'll want to pick colors that look different from each other.  In some cases you might want to avoid dithered colors, since they look too broken on really thin lines.  For example, on my printer I like the following colors: black, red, yellow, green, cyan, and magenta.

The set color rgb .red. .green. .blue. command

This command sets the color using the red-green-blue color model.  If you are familiar with how colors add (e.g. red plus green yields yellow), then you might like this, but most people find it easier to use the set color hsb ... style described below.

Set the individual color components as follows.  The numbers .red., .green. and .blue. range from 0 (for no contribution of that color component to the final color) to 1 (for maximal contribution).  Values less than 0 are clipped to 0; values greater than 1 are clipped to 1. EXAMPLES:

     set color rgb 0   0   0  # black
     set color rgb 1   1   1  # white
     set color rgb 1   0   0  # bright red
     set color rgb 0.5 0   0  # dark red
     set color rgb 0   1   0  # pure green
     set color rgb 1   1   0  # yellow: red + green

The set color hsb .hue. .saturation. .brightness. command

In this color model, the color ("hue") is specified with a single parameter.  Many people find this easier than using the corresponding rgb command.

Set the individual color components as follows.  The numbers .hue., .saturation. and .brightness. range from 0 to 1.  The color, represented by .hue., ranges from 0 for pure red, through 1/3 for pure green, and 2/3 for pure blue, and back to 1 again for pure red.  (HINT: It is a good idea to limit the total range of hue you use to 2/3, instead of 1; otherwise you'll get confused by (nearly) repeated colors at the crossover.  For example, limit the hue to range from 1/3 to 1, or 0 to 2/3.)  The purity of the color, represented by .saturation., ranges from 0 (none of the hue is visible) to 1 (the maximal amount is present).  Less saturated colours are like those you would get from mixing black paint into colored paint.  The brightness of the color, represented by .brightness., ranges from 0 (black) to 1 (maximal brightness).  Lowering brightness is like decreasing the intensity of the light you shine on a painting.

Hue, saturation, and brightness values are all clipped to the range 0 to 1. EXAMPLES:

     set color hsb 0    1   1  # pure, bright red
     set color hsb 0    1 0.5  # half black, half red
     set color hsb .333 1   1  # pure, bright green

X-Y Plots
*********

Linegraphs
==========

The following Gri commands will draw a linegraph.  For the output graph (Getting More Control).

This plots a simple linegraph:

     # Example 1 -- Linegraph using data in a separate file

     open example1.dat      # Open the data file
     read columns x y       # Read (x,y) columns
     draw curve             # Draw data curve
     draw title "Example 1" # Title above plot

Here's what the command lines mean:

  * The first line is a comment.  Anything to the right of a hash-mark # is considered to be a comment.  (This symbol is also called a "pound".)

  * The second line is blank.  Gri ignores blank lines between commands.

  * open example1.dat tells Gri to open the indicated file (in the current directory) as an input data file.  You can specify files outside the current directory by using conventional unix-shell pathnames (e.g., open ~/data/TS/section1/T_S.dat or open ../data/file.dat).  You can even use "synonyms" (Synonyms.) in filenames, as in open \BASENAME.dat.

  * read columns x y tells Gri to start reading columnar data, the first column being x, the second y.  x and y are predefined names for whatever ends up on the horizontal and vertical axes.

     The number of data needn't be specified.  Gri reads columns until a blank line or end-of-file is found.  You can tell Gri how many lines to read with a command like read columns 10 x y.  Multiple datasets can reside within one file; provided that they are separated by a single blank line, Gri can access them by multiple read commands.

     Like C, Gri expects numbers to be separated by one or more spaces or tabs.  Commas are not allowed.  If the columns were reversed, the command would be read columns y x.  If there were an initial column of extraneous data, the command would be read columns * x y, or read columns x=2 y=3 (Read Columns).

  * draw curve tells Gri to draw a curve connecting the points in the x and y columns. A nice scale will be selected automatically.  (You can change this or any other plot characteristics easily, as you'll see later.)

  * draw title tells Gri to write the indicated string centered above the plot. The title must be enclosed in quotes.

  * quit tells Gri to exit.

Gri will draw axes automatically, and pick its own scales.

If you wish to draw several curves which cross each other, you should try using draw curve overlying instead of draw curve.  This will make it easier to distinguish the different curves.

Scattergraphs
=============

This section contains two examples, the first being a fuller explanation of all the bells and whistles, the second being a simple explanation of how to get a very quick plot, given just a file containing a matrix of grid data.

To get a scattergraph with symbols at the data points, substitute draw symbol for draw curve.  Both symbols and a curve result if both draw curve and draw symbols are used. See Getting More Control for an example.

By default, the symbol used is an x.  To get another symbol, use a command like draw symbol 0 or draw symbol plus.

To change the symbol size from the default of 0.2 cm use commands like set symbol size 0.1 to set to 1 mm (Set Symbol Size).

Coding data with symbols
------------------------

To get different symbols for different data points, insert symbol codes from the above list as a column along with the x-y data, and substitute the command read columns x y z, and then draw them with draw symbol.  Gri will interpret the rounded-integer values of the z columns as symbol codes.  Note that even if you've read in a z column which you intend to represent symbols, it will be overridden if you designate a specific symbol in your draw symbols command; thus draw symbol 0 puts a + at the data points whether or not you've read in a symbol column.

Drawing a symbol legend
-----------------------

The following example shows how you might write a symbol legend for a plot.  The legend is drawn 1 cm to the right of the right-hand side of the axes, with the bottom of the legend one quarter of the way up the plot; Draw Symbol Legend.  The lines in the legend are double-spaced vertically.  To change the location of the legend, alter the .legend_x. = and .legend_y. = lines.  To change the spacing, alter the .legend_y. += line.

     set x axis -1 5 1
     set y axis -1 5 1
     read columns x y z
     0 0 0
     1 1 1
     2 2 2
     3 3 3

     draw symbol

     # Legend
     .leg_x. = {rpn ..xmargin.. ..xsize.. + 1 +}
     .leg_y. = {rpn ..ymargin.. ..ysize.. 4 / +}
     draw symbol legend 0 "Foo" at .leg_x. .leg_y. cm
     .leg_y. += {rpn "M" ascent 2 *}
     draw symbol legend 1 "Bar" at .leg_x. .leg_y. cm
     .leg_y. += {rpn "M" ascent 2 *}

Coding data with symbol colors
------------------------------

To get different colors for different symbols, read a color code into the z column, and do for example draw symbol bullet color hue z. The numerical color code ranges from 0 (red) through to 1, passing through green at 1/3 and blue at 2/3.

Formula Plots
=============

There are two methods for formula graphs.

 1. Use the system yourself. Do as in this example:

          open "awk 'BEGIN{for(i=0;i<3.141;i+=0.05)\
              {print(i,cos(i))}}' |"
          read columns x y
          close
          draw curve

 2. Let Gri calculate things for you

     The simplest is to let Gri calculate things for you with the create columns from function command (Create).  The command assumes that you have defined the synonym called \function which defines y in terms of x.

     Gri uses the program awk to create the columns, and cannot work without it.

     Here is an example of using create columns from function:

          show "First 2 terms of perturbation expansion"
          set y axis name horizontal
          set y name "sea-level"
          set x name "$\omega$t"

          \b = "0.4" # perturbation parameter b=dH/H
          \xmin = "0"
          \xmax = "6.28"
          \xinc = "3.14 / 20"
          \function = "cos(x)"
          set x axis \xmin \xmax
          create columns from function
          draw curve
          draw title "SOLID LINE  \function"

          \function = "(cos(x)+\b/2*(1-cos(2*x)))"
          create columns from function
          set dash 1
          draw curve
          draw title "DASHED LINE \function"

          draw title "b = \b"

     Here's another example, in which the curve y = 1/(\int + \sl*x) is drawn through some data.  Note how sprintf is used to set \xmin and \xmax using the scales that Gri has determined in reading the data.

          open file.data
          read columns x y
          close
          draw symbol bullet
          \int = "-0.1235"
          \sl = "0.003685"
          sprintf \xmin "%f" ..xleft..
          sprintf \xmax "%f" ..xright..
          \function = "1/(\int + x * \sl)"
          create columns from function
          draw curve

Contour Plots
*************

Contour plots can be done with either pregridded data or randomly distributed (ie, ungridded) data.

Pre-gridded Data
================

This section presents two examples of contouring pre-gridded data, the first example illustrating a boilerplate program to contour data stored in a simple matrix form in a file, the second example illustrating a case with more control of the details (e.g., a nonuniform grid).

Simple example
--------------

This example was hardwired to know the size of the grid, etc.  Here's an example which is more general, in that it determines the dimensions of the grid data from using unix system commands.  Note that the grid is set to run from 0 to 1 in both x and y; you'll most likely want to change that after you see the initial plot, but this should get you started.

     \file = "somefile.dat"
     \rows = system wc \file      | awk '{print $1}'
     \cols = system head -1 \file | awk '{print NF}'
     set x grid 0 1 /\cols
     set y grid 0 1 /\rows
     open \file
     read grid data \rows \cols
     close
     draw contour

Complicated example
-------------------

To get a simple contour graph based on pre-gridded data, with full control of axes, etc, do something like this:

     # Example 4 -- Simple contour graph

     #
     # Read x-grid; blank-line means stop reading.
     read grid x
     0
     .2
     1

     # Note that the x-grid was irregular.  The y-grid
     # in this example is regular, so we can just set
     # it to range from 10 to 20, incrementing by 2.5.
     set y grid 10 20 2.5
     # Thus we now have a grid 3 wide and 5 high.  Let's
     # read the actual data now.
     read grid data
     1 2 3
     2 3 4
     3 4 5
     4 5 6
     5 6 7

     # Now draw contours (automatically set; we could
     # have done `draw contour 2' to draw contour for
     # value 2 or `draw contour 1 10 2' to draw contours
     # ranging from 1 to 10 with an increment of 2.)
     draw contour
     draw title "Example 4"

Here several new things have been introduced.

First, you've got to define a grid in xy space.  This example uses a non-uniform x-grid, and reads it in from the commandfile.  In this form, the blank line is essential; it tells Gri that the end of data has been located; if you like, you can specify the number of lines to read, as in read grid x 3.

The y-grid for this example is uniform, however, so it may be specified with the set y grid command.  It obtains values (10, 12.5, 15, 17.5, 20).  The set x|y grid commands accept negative increments. Furthermore, it is possible to specify the number of steps, rather than the increment size, by putting / before the third number; thus set x grid 0 1 /5 and set x grid 0 1 0.2 are equivalent.

Having defined a grid, it is time to read in the gridded data.  Here this is done with the read grid data command.  Since Gri already knows the grid dimensions, it will read the data appropriately.  You could also have told it (read grid data 3 5).

The first dataline is the top of the y-grid.  In other words, the data appear in the file just as they would on the graph, assuming that the x-grid and y-grid both increase.

Sometimes you want to read in the transpose of a matrix.  Gri lets you do that.  If the bycolumns keyword is present at the end of the read grid command, the first dataline will contain the first column, of the data.

If you have an extraneous column of data to the left of your data matrix, do read grid data * 2 3

Now Gri has the grid in its head.  We tell it to draw some contours with the draw contour command.   As the comments in the example show, the contour values will be selected automatically, but you can alter that.

Ungridded data
==============

When you have f=f(x,y) points at random x and y, you must cast them onto a grid to contour them.  This is a difficult problem.  There are many ways to grid data, and all have both good and bad features.  You should try various methods, and various settings of the parameters of the methods.  If you have a favorite gridding method that you prefer, you should probably pre-grid the data yourself.  If not, Gri can do it for you.  Gri has two methods for doing this, the ``boxcar'' method and the ``objective analysis'' method.  Each method puts holes in the grid wherever there are too few data to map to grid points, unless you specifically ask to fill in the whole grid.

The next two sections show first an example, then a discussion of the methods and how to use them.

Example
-------

This example uses data taken from Figure 5 of S. E.  Koch and M. DesJardins and P. J. Kocin, 1983.  ``An interactive Barnes objective map anlaysis scheme for use with satellite and conventional data,'', J. Climate Appl.  Met., vol 22, p. 1487-1503.  Readers should compare Figures 5 and 6 of that paper to the results shown here.

     # Example 5 - Contouring ungridded data, from figure
     # 5 of Koch et al., 1983, J. Climate Appl. Met.,
     # volume 22, pages 1487-1503.
     open example5.dat
     read columns x y z
     close
     set x size 12
     set x axis 0 12 2
     set y size 10
     set y axis 0 10 2
     draw axes
     set line width symbol 0.2
     set symbol size 0.2
     draw symbol bullet
     set font size 8
     draw values
     set x grid 0 12 0.25
     set y grid 0 10 0.25

     # Use default method (Barnes)
     convert columns to grid

     set font size 10
     draw contour 0 40 2
     set font size 12
     draw title "Example 5 -- wind (Fig5 Koch et al, 1983)"

Discussion of Methods
---------------------

The various commands for converting columns to a grid are given in (Convert Columns To Grid).  Generally, the Barnes method is best.

Image Plots
***********

Gri can read in images stored in various formats.  It can also create image data internally, by converting gridded data, which is quite handy in some contouring applications.

Note: if your diagram is to be reproduced by a journal, it is unlikely that the reproduction will be able to distinguish between any two graylevels which differ by less than 0.2.  Also, graylevels less than 0.2 may appear as pure black, while those of 0.8 or more may appear as pure white.  These guidelines are as specified by American Geophysical Union (publishers of J. Geophysical Res.), as of 1998.

Reading and Creating Image Data
===============================

Gri can do black and white image plots, such as satellite images.  There are several ways to create image data in Gri

  * Create images from gridded data using convert grid to image.  For examples see Grayscale Images), Combination, and Contouring.

  * Read raw ascii image data files.  Use read grid.

  * Read PGM (portable graymap) ascii files.  (That is, a file with magic characters P1 or P3 at the start.)  Use the read image pgm command, for a file opened in ascii mode with open filename.

  * Read raw binary data, with or without headers.  Use read image, after skipping any header bytes using the skip command, for a file opened in binary mode with open filename binary.

  * Read a Sun ``rasterfile'' file (but only in uncompressed form).  Use read image rasterfile for a file opened in binary mode with open filename binary.

  * Read a PGM (portable graymap) binary file.  (A file with magic characters P2 or P4 at the start.)  Use the read image pgm for a file opened in binary mode with open filename binary.

  * Aside: Images can be converted to grids (for contouring) using convert image to grid (Convert).

Once the image is created, its grayscale/colorscale may be manipulated with the commands set image grayscale and set image colorscale, which permit linear and histogram-equalized blendings over the grayscale or color range, or with read image grayscale and read image colorscale, which permit reading in the grayscale or color values individually, one for each of the 256 pixel values.

It is important to understand the structure of image data.  Gri works only with 8-bit image data.  This means that a given pixel of the image may have only one of 256 possible values.  The example below uses a satellite image of surface temperature.  The suppliers of the data dictate that pixel value 0 corresponds to a temperature of 5C, and a pixel value of 255 corresponds to 30.5C, so the resolution is 0.1C per pixel value.  This resolution will be apparent if the output of the example below is previewed on a grayscale/color monitor --- notice the quantization in the palette.  This resolution issue is not very important with satellite images, since you have to use what you are given by the suppliers of the data.  However, the issue is very important when you are converting grid data to images.  When Gri converts grid data to image data, it neccessarily discards information, because the grid data have resolution to about 6 digits, whereas the image data have only 8-bit (2-3 digit) resolution.  The set image range commands determines the range of this 8-bit resolution in terms of user units. All other things being equal, it would be preferable to use the smallest range consistent with the range of your data.  If your grid data ranged from 0 to 1, say, you might set image range 0 1.  This would give a resolution in the image of 1/255 in the user units.  But, when Gri converts the grid into an image, it will clip all data outside the indicated range.  In this case, any data greater than 1 in the grid would translate to exactly 1 in the image.  Naturally there is a tradeoff between having a range large enough to encompass any data in the grid, and a range small enough to yield adequate resolution.  In most cases, 8-bit resolution will be adequate, but it is good to be aware of the limitations.  One should always draw image palette, and check it on a color monitor for bandedness, which is a sign of resolution problems.

About The PostScript Output
===========================

Programmers Note: Gri inserts some special comments in the PostScript file, to help programmers extract the image data; to extract the information, you'll have to understand how PostScript handles images. Gri inserts a single comment line before a line ending in the token im:

     %BEGIN_IMAGE
     170.70 170.70 534.86 534.86 128 128 im

The first four numbers are the (x,y) locations of the lower-left and upper-right corners of the image, in units of points on the page (72 points = 1 inch).  The fifth and sixth numbers are the width of the image and the height of the image.  The keyword im is always present on this line.  Gri inserts the following comment line at the end of the image data

     %END_IMAGE

Example (Satellite image)
=========================

Here's an example that will plot different types of images, depending on your answers to query questions.  The file called \filename is the data file, in binary format with one byte (unsigned char in C) for each pixel, stored with the northwest pixel first, and the pixel to the east of that next. The file called \mask is in the same format, and the numbers are 0 if the point is over the sea and 1 if over land.  The mask file is used in computing the histograms, which is done if \histo is 1.

The file in this example covers 128 * 128 pixels over the Gulf of Maine. The numbers in \filename correspond to surface temperatures according to the equation

     T = 5 + 0.1 * pixel_value

which explains the following lines in the command file:

     \0val = "5"             # 0 in image
     \255val = "30.5"        # 255 in image

Depending on \histo, the graymap will be linear or histogram-enhanced. The histogram method consists of dividing the cumulative histogram for the values in the image up into 256 levels, and assigning a graylevel to each.  This has the effect of creating maximal contrast in all ranges of graylevel. It points up features really well, but it is a nonlinear mapping, so it is not good for telling you where gradients are strong or weak.

Examples are shown for linear mapping and histogram mapping.

     # Example 6 -- Plot IR image of Gulf of Maine
     # Define characteristics of norda images
     # Note that the pixel to temperature conversion formula is
     #
     #   Temperature = 5C + pixel_value / 10
     #
     # where pixel_value ranges from 0 to 255.  Thus, a pixel value of 0
     # corresponds to a temperature of 5C, and 255 corresponds to 30.5C;
     # this is why the limits \0val and \255val, for use by the `set image
     # range' command, take on these values.
     \0val = "5"                     # 0 in image
     \255val = "30.5"                # 255 in image
     .rows. = 128
     .cols. = 128
     .pixel_width. = 2
     .km. = {rpn .cols. .pixel_width. *}

     # get filenames
     query \filename "Name image file" ("example6image.dat")
     query \maskname "Name mask  file" ("example6mask.dat")

     # get data, then mask, each in 8-bit image format
     open \filename 8bit
     set image range \0val \255val
     read image .rows. .cols. box 0 0 .km. .km.
     close
     open \maskname 8bit
     read image mask .rows. .cols.
     close

     # find out what grayscale method to use
     query \histo "Do histogram enhancement? (yes|no)" ("no")
     query \minT  "T/deg for white on page?          " ("10")
     query \maxT  "T/deg for black on page?          " ("15")
     \incT = "1"

     # set up scales.
     set x size 12.8
     set y size 12.8
     set x name "km"
     set y name "km"
     set x axis 0 .km. 32
     set y axis 0 .km. 32

     # plot image, grayscale, and histogram
     if {"\histo" == "yes"}
         set image grayscale using histogram black \maxT white \minT
     else
         set image grayscale black \maxT white \minT
     end if
     draw image
     draw image palette left \minT right \maxT increment \incT
     draw image histogram
     if {"\histo" == "yes"}
         draw title "Example 6: grayscale histogram enhanced"
     else
         draw title "Example 6: grayscale linear \minT to \maxT"
     end if

Real-world examples
*******************

The example files in this manual should be available to you directly, having been installed with Gri; if not, ask your system manager to check the FTP site.

Additionally, I've collected a few real life examples here.  Other sources are the Gri cookbook, available at http://gri.sourceforge.net/gri-cookbook/index.html.

Box plots
=========

Box plots were invented by Tukey for eda (exploratory data analysis). They show nonparametric statistics.  The centre of the box is the median.  The box edges show the first quartile (q1) and the third quartile (q3).  The distance from q3 to q1 is called the inter-quartile range.  The whiskers (lines with crosses on them) extend to the furthest points still within 1.5 inter-quartile ranges of q1 and q3.  Beyond the whiskers, all outliers are shown, in open circles up to a distance of 3 inter-quartile ranges beyond q1 and q3, and in closed circles beyond that.  Below is an example that uses a "new command" to define each box plot (Adding New Commands).

     # Example 7 -- Box plots of mixing efficiency vs density ratio (meddy)

     `Draw y boxplot from \file at .x.'
     Draw a y boxplot for data in given file, at given
     value of x.
     {
         open \.word4.
         read columns * y
         close
         draw y box plot at \.word6.
     }
     if !..publication..
         draw time stamp
     end if
     set x axis 1 3 1 0.1
     set x name "Density Ratio, $R_\rho$"
     set x margin 4
     set y axis -2 1 1
     #
     # Must fool gri into not drawing the axes, because the y data
     # are already in logspace.
     draw axes none
     Draw y boxplot from example7a.dat at 1.3
     Draw y boxplot from example7b.dat at 1.4
     Draw y boxplot from example7c.dat at 1.5
     Draw y boxplot from example7d.dat at 1.6
     Draw y boxplot from example7e.dat at 1.7
     Draw y boxplot from example7f.dat at 1.8
     Draw y boxplot from example7g.dat at 1.9
     delete y scale
     set y name "Efficiency, $\Gamma$"
     set y type log
     set y axis 0.01 10 1
     draw axes
     draw title "Example 7 -- Box plot"

Contouring
==========

This example plots a section of dT/drho vs x and rho (actually, sigma-t, as the label indicates).  The contours are unlabelled; I'm only interested in the zero crossings.

There are some other useful tricks in this example, such as calling awk and wc from the unix system.

(In the plot shown, all query questions were answered with carriage return, yielding the defaults; the -p flag was specified on execution, so the time stamp was not drawn.)

     # Example 8 -- Plot T=T(x,rho) section of eubex data

     `Initialize Parameters'
     {
         \FILE_DATA = "example8a.dat" # T vs rho
         \FILE_LOCN = "example8b.dat" # section distances
         set missing value -99.0
         #
         # Following values from ~/eubex/processing/to_rho_bins/do_rho_inter
         \RHO_MIN = "28.1"
         \RHO_MAX = "27.5"
         \RHO_INC = "-0.002"
         \NY = "301"
         \xmin = "350"
         \xmax = "0"
         \xinc = "-100"
         \ymin = "28.1"
         \ymax = "27.8"
         \yinc = "-0.1"
         \zmin = "0"
         \zmax = "2.5"
     }
     `Initialize Axes'
     /*
     Set up axes
     */
     {
         set x name "km"
         set x size 10
         set x axis \xmin \xmax \xinc
         set y name "$\sigma_T$"
         set y size 5
         set y axis name horizontal
         set y axis \ymin \ymax \yinc
         set y format "%.1f"
     }
     `Initialize Files'
     {
         query \data "Data file?   " ("\FILE_DATA")
         query \locn "Station locn?" ("\FILE_LOCN")
     }
     `Read Data'
     {
         # Read x-locations
         system awk '{print $2}' < \locn > TMP
         system wc TMP | awk '{print $1}' > NUM
         open NUM
         read .gridx_number.
         close
         system rm NUM
         open TMP
         read grid x .gridx_number.
         close
         system rm TMP
         # Create y-locations
         set y grid \RHO_MIN \RHO_MAX \RHO_INC
         #
         # Read data
         open \data
         read grid data \NY .gridx_number.
         close
     }
     `Plot Contours'
     {
         set graylevel .contour_graylevel.
         set clip on
         set line width 0.5
         draw contour -3 3 0.25 unlabelled
         #
         # wide line at 0 degrees
         set line width 2
         draw contour 0 unlabelled
     }
     `Plot Image And Maybe Contours'
     {
         \imagefile = "image"
         set image range \zmin \zmax
         convert grid to image box \xmin  \ymin \xmax \ymax
         query \dohisto "Do histogram scaling? (yes|no)" ("yes")
         \incs = "no"
         if {"\dohisto" == "yes"}
     	set image grayscale using histogram
         else
     	\zinc = "0.25"
     	query \incs "In linear scaling, band at an increment of \zinc?" ("yes")
     	if {"\incs" == "yes"}
     	    set image grayscale black \zmin white \zmax increment \zinc
     	else
     	    set image grayscale black \zmin white \zmax
     	end if
         end if
         write image rasterfile to \imagefile
         show "wrote image rasterfile `\imagefile '"
         draw image
         draw image palette
         query \do_contours "Do contours as well (yes|no)" ("yes")
         if {"\do_contours" == "yes"}
     	Plot Contours
         end if
         draw title "Example 8 -- \data black=\zmin white=\zmax"
         if {"\dohisto" == "yes"}
     	draw title "Histogram enhanced grayscales"
         else
     	if {"\incs" == "yes"}
     	    draw title "Grayscale banded at intervals of \zinc"
     	end if
         end if
     }
     Initialize Parameters
     Initialize Axes
     Initialize Files
     Read Data
     query \doimage "Draw image (yes|no)" ("no")
     if {"\doimage" == "yes"}
         .contour_graylevel. = 1	# white contours
         Plot Image And Maybe Contours
     else
         .contour_graylevel. = 0	# black contours
         Plot Contours
         draw title "Example 8"
     end if

Image created from coarsely gridded data
========================================

This example reads gridded ascii station data (Read Data), creates an interpolated image (convert grid ...), and then plots the image.

There are some other useful tricks in this example, such as calling awk and wc from the unix system.

(In the plot shown, all query questions were answered with carriage return, yielding the defaults; the -p flag was specified on execution, so the time stamp was not drawn.)

     # Example 9 -- Plot dTdrho-rho section

     `Initialize Parameters'
     {
         \FILE_DATA = "example9a.dat" # T vs rho
         \FILE_LOCN = "example9b.dat" # section distances
         #
         # Following values from ~/eubex/processing/to_rho_bins/do_rho_inter
         \RHO_MIN = "28.1"
         \RHO_MAX = "27.5"
         \RHO_INC = "-0.002"
         \NY = "301"
         set missing value -99.0
         \xmin = "350"
         \xmax = "0"
         \xinc = "-100"
         \ymin = "28.1"
         \ymax = "27.8"
         \yinc = "-0.1"
         \zmin = "-10"		# black
         \zmax = "0"			# white
     }
     `Initialize Axes'
     Set up axes.
     {
         set x name "km"
         set x size 10
         set x axis \xmin \xmax \xinc
         set y size 5
         set y name "$\sigma_T$"
         set y axis name horizontal
         set y axis \ymin \ymax \yinc
         set y format %.1lf
         draw axes none
     }
     `Initialize Files'
     {
         query \data "Data file?   " ("\FILE_DATA")
         query \locn "Station locn?" ("\FILE_LOCN")
     }
     `Read Data'
     {
         # Read x-locations
         system awk '{print $2}' < \locn > TMP
         system wc TMP | awk '{print $1}' > NUM
         open NUM
         read .gridx_number.
         close
         system rm NUM
         open TMP
         read grid x .gridx_number.
         close
         system rm TMP
         # Create y-locations
         set y grid \RHO_MIN \RHO_MAX \RHO_INC
         #
         # Read data
         open \data
         read grid data \NY .gridx_number.
         close
     }
     Initialize Parameters
     Initialize Axes
     Initialize Files
     Read Data
     set image range \zmin \zmax
     set image colorscale hsb 0 1 1 \zmin   hsb .6 1 1 \zmax
     convert grid to image box \xmin  \ymin \xmax \ymax
     #
     # Draw the image, then draw the axes.  Note that the image has
     # extends beyond the axes frame, so we will turn clipping
     # on before drawing it, to make a clean picture.
     set clip postscript on
     draw image
     set clip postscript off
     draw axes

     #
     # All done.
     draw title "Example 9"
     if {"\dohisto" == "yes"}
         draw title "Histogram enhanced grayscales"
     end if

Combination of image and contour
================================

The following example reads gridded data and creates an image as in the previous example, but also superimposes unlabelled white contour lines.

(In the plot shown, all query questions were answered with carriage return, yielding the defaults; the -p flag was specified on execution, so the time stamp was not drawn.)

     # Example 10 -- Draw image plot of flushing of dye out of cove
     if !..publication..
         draw time stamp
     end if
     \file = "example10.dat"
     query \contours "Superimpose contours? (yes|no)" ("yes")
     query \file     "Input file name               " ("\file")
     open \file
     read line \header
     read \D
     read .nx.
     read .ny.
     set x name "distance along cove"
     set y name "time"
     set x grid 0 1 /.nx.
     set x axis 0 1 0.5 0.1
     set y grid 0 .ny. / .ny.
     set y axis 0 .ny.
     read grid data * * .ny. .nx.
     set image range 0 20
     set image grayscale black 20 white 0 increment 5
     convert grid to image
     draw image
     if {"\contours" == "yes"}
         set graylevel 1.0
         draw contour 0 20 1 unlabelled
         set graylevel 0.0
     end if
     draw axes
     draw image palette left -1 right 21 increment 5
     draw title "Example 10 -- file=\file header=`\header'"

     # Example 10color -- Draw color image plot

     # Test various colorscales.
     # INSTRUCTIONS: Uncomment one of the following '\scale = ' statements

     # CASE 1: From black at high values to white at low values
     #\scale = "rgb 0 0 0 20.0 rgb 1 1 1  0.0 increment 5"

     # CASE 2: From skyblue at 20 to tan for 0; traverse RGB space
     #         See also case 5, which names the colors.
     #\scale = "rgb 0.529 0.808 0.922 20.0 rgb 0.824 0.706 0.549 0.0 increment 5"

     # CASE 3: From skyblue at 20 to tan for 0; traverse HSB space
     #         Is it just me, or is this uglier than case 2?
     #\scale = "hsb 0.548 0.426 0.922 20.0 hsb 0.095 0.334 0.824 0.0 increment 5"

     # CASE 4: Use a spectrum; traverse HSB space
     #\scale = "hsb 0 1 1 20.0 hsb 0.6666 1 1  0.0 increment 5"

     # CASE 5: From skyblue to tan, traversing RGB space (by default)
     #         (Compare case 2, which uses similar endpoints, with
     #         colors specified with RGB values, and larger increment.)
     #\scale = "skyblue 20.0 tan 0.0 increment 2"

     # CASE 6: From skyblue to tan, traversing RGB space (by default)
     #         Compare 2 and 5; note this has continuous increment
     #\scale = "skyblue 20.0 tan 0.0"

     # CASE 7: From blue to brown
     \scale = "blue 20.0 brown 0.0 increment 2.5"

     open example10.dat
     read line \header
     read \D
     read .nx.
     read .ny.
     set x name "distance along cove"
     set y name "time"
     set x grid 0 1 /.nx.
     set x axis 0 1 0.5 0.1
     set y grid 0 .ny. / .ny.
     set y axis 0 .ny.
     read grid data * * .ny. .nx.
     set image range 0 20
     convert grid to image
     set image colorscale \scale
     draw image

     # Draw contours in white ink
     set graylevel 1.0
     draw contour 0 20 1 unlabelled
     set graylevel 0.0

     draw axes                               # redraw in case whited out
     draw image palette left -1 right 21 increment 5
     set font size 9

     # Title tells what method used
     draw title "Used `draw image colorscale \scale'"

Fancy x-y linegraph
===================

The following code shows a fancy plot with lots of bells and whistles.

     # Example 11 -- Fancy plot
     # Pen sizes, etc.
     #
     .thin. = 0.5                    # for whole data set
     .thick. = 2                     # for bravo time period
     .gray_for_guiding_lines. = 0.75 # for guiding lines
     .tmin. = 1964                   # time axis
     .tmax. = 1974
     .tinc. = 5
     .tincinc. = 1
     .missing_value. = -9
     \file = "./example11.dat"
     #
     # Guiding lines to draw on both panels.
     #
     .1xl. = 1962
     .1yb. = -3
     .1xr. = 1968
     .1yt. = 3
     .1slope. = {rpn .1yt. .1yb. - .1xr. .1xl. - /}
     .1intercept. = {rpn .1yb. .1slope. .1xl. * -}
     .2xl. = 1966.4
     .2yb. = 3
     .2xr. = 1980
     .2yt. = -1
     .2slope. = {rpn .2yt. .2yb. - .2xr. .2xl. - /}
     .2intercept. = {rpn .2yb. .2slope. .2xl. * -}
     #
     # PANEL 1: Bravo time period.
     #
     set x margin 3
     set x size 15
     set y margin 3
     set y size 5
     # Draw border big enough for this and next panel.
     draw border box {rpn ..xmargin.. 2 -} \
         {rpn ..ymargin.. 2 -} \
         {rpn ..xmargin.. ..xsize.. + 2 +} \
         {rpn ..ymargin.. ..ysize.. 2 * 3 + + 2 +} \
         0.2 0.75
     set missing value .missing_value.
     set ignore error eof
     set x name "Year"
     set x axis .tmin. .tmax. .tinc. .tincinc.
     set y name "Area / 10$^5$km$^2$"
     set y axis -3 3 1
     draw axes
     #
     # Draw index lines 1 and 2.
     #
     # Upward sloped line.
     set line width .thin.
     set graylevel .gray_for_guiding_lines.
     if {rpn .1intercept. ..xright.. .1slope. * + ..ytop.. <}
         draw line from              \
             ..xleft..               \
             {rpn .1intercept. ..xleft.. .1slope. * +} \
             to                      \
             {rpn ..ytop.. .1intercept. - .1slope. /} \
             ..ytop..
     else
         draw line from              \
             ..xleft..               \
             {rpn .1intercept. ..xleft.. .1slope. * +} \
             to                      \
             ..xright..              \
             {rpn .1intercept. ..xright.. .1slope. * +}
     end if
     set graylevel 0
     #
     # Downward sloped line.
     set line width .thin.
     set graylevel .gray_for_guiding_lines.
     if {rpn .2intercept. ..xleft.. .2slope. * + ..ytop.. <}
         draw line from              \
             {rpn ..ytop.. .2intercept. - .2slope. /} \
             ..ytop..                \
             to                      \
             ..xright..              \
             {rpn .2intercept. ..xright.. .2slope. * +}
     else
         draw line from              \
             ..xleft..               \
             {rpn .2intercept. ..xleft.. .2slope. * +} \
             to                      \
             ..xright..              \
             {rpn .2intercept. ..xright.. .2slope. * +}
     end if
     set graylevel 0
     #
     # Finally, draw the data curve on top, after first
     # whiting out a background.
     set input data window x .tmin. .tmax.
     open \file
     read columns x y
     close
     y /= 1e5
     set line width ..linewidthaxis..
     draw zero line
     set line width {rpn .thick. 3 *}
     set graylevel 1
     draw curve
     set graylevel 0
     set line width .thick.
     draw curve

     #
     # PANEL 2: Longer timescale.
     #
     delete x scale
     set x margin bigger 5
     set x size 10
     set x name ""
     set y name ""
     set y margin bigger {rpn ..ysize.. 3 +}
     #
     # Draw long data set in thin pen.
     set input data window x off
     open \file
     read columns x y
     close
     y /= 1e5
     #
     # Draw guiding lines, axes, etc.
     set x axis 1952 1980 5 1
     draw axes frame
     set line width .thin.
     set graylevel .gray_for_guiding_lines.
     draw line from .1xl. .1yb. to .1xr. .1yt.
     draw line from .2xl. .2yb. to .2xr. .2yt.
     set graylevel 0
     set line width ..linewidthaxis..
     draw zero line

     draw x axis at bottom
     .old. = ..fontsize..
     set font size 0
     draw y axis at left
     set font size .old.
     delete .old.
     #
     # Draw full curve (first whiting out region around it).
     set line width {rpn .thin. 4 *}
     set graylevel 1
     draw curve
     set graylevel 0
     set line width .thin.
     draw curve
     #
     # Draw bravo time period (first whiting out region around it).
     set input data window x .tmin. .tmax.
     open \file
     read columns x y
     close
     y /= 1e5
     set line width {rpn .thick. 3 *}
     set graylevel 1
     draw curve
     set graylevel 0
     set line width .thick.
     draw curve
     #
     # Done
     set font size 20
     \label = "Example 11 (Arctic ice anomaly)"
     draw label "\label" at          \
         {rpn 8.5 2.54 * "\label" width - 2 /} \
         {rpn ..ytop.. yusertocm 0.7 +} \
         cm
     if !..publication..
         draw time stamp
     end if

Legends and annotated lines
===========================

The following example shows how to handle annotated curves and legends.

     # Example 12 -- Linegraph with key inside plot
     set font size 10                # points (1in = 72pt)
     set x size 10                   # cm
     set y size 10                   # cm
     set x name "Height"
     set y name "Total Energy"

     # Following axis setups not necessary; will autoscale if you
     # remove these.
     set x margin 3
     set x axis 800 960 20
     set y margin 3
     set y axis -0.4 1 0.2

     # Read data.  Format is columns (x, y1, y2, y3, y4)
     open example12.dat
     read columns x y
     draw curve
     draw label for last curve "1"

     rewind
     set line width {rpn ..linewidth.. 1.5 *}
     read columns x * y
     draw curve
     draw label for last curve "2"

     rewind
     set line width {rpn ..linewidth.. 1.5 *}
     read columns x * * y
     draw curve
     draw label for last curve "3"

     rewind
     set line width {rpn ..linewidth.. 1.5 *}
     read columns x * * * y
     draw curve
     draw label for last curve "4"

     # Draw the key.
     # NOTES:
     # (1) This key is inside the plot; its location was chosen
     #     after looking at the data.  To put the key in a different
     #     location, alter the .key_topleft_x. and .key_topleft_y.
     #     variables.  For example, you could put the key to the
     #     right of the plot by changing the next line to:
     #     `.key_topleft_x. = {rpn ..xsize.. 0.5 +}'
     # (2) The variable .dy_inc. is the spacing between lines in
     #     the key.  It should be OK even if you change the
     #     font size above.
     .key_topleft_x. = 0.5           # cm right of left axis
     .key_topleft_y. = 0.5           # cm below top axis
     .dy_inc. = {rpn ..fontsize.. pttocm 1.5 *}

     draw label "1 = Model 1A" at    \
         {rpn ..xleft.. xusertocm .key_topleft_x. +} \
         {rpn ..ytop.. yusertocm .key_topleft_y. -} cm

     .key_topleft_y. += .dy_inc.
     draw label "2 = Model 2A" at    \
         {rpn ..xleft.. xusertocm .key_topleft_x. +} \
         {rpn ..ytop.. yusertocm .key_topleft_y. -} cm

     .key_topleft_y. += .dy_inc.
     draw label "3 = Model 1B" at    \
         {rpn ..xleft.. xusertocm .key_topleft_x. +} \
         {rpn ..ytop.. yusertocm .key_topleft_y. -} cm

     .key_topleft_y. += .dy_inc.
     draw label "4 = Model 2B" at    \
         {rpn ..xleft.. xusertocm .key_topleft_x. +} \
         {rpn ..ytop.. yusertocm .key_topleft_y. -} cm

     draw title "Example 12 -- Total heating vs height of boundary layer"

Drawing gray polygons
=====================

The following example shows how to draw polygons of a graylevel that is read in.  It also draws a bullet (within the polygon).  See the help lines at the start.

     `Draw Polygon And Bullet'
     Draw a polygon of a given graylevel, with a bullet
     (black dot) at an indicated location.  The polygon
     coordinates are read in by this command, as are
     the graylevel and the location of the bullet.

     Variables used:
       .black.
       .white.

     Input data read:

     line   1:
       A code (which is ignored) and a graylevel
       to draw the polygon with. The value for this
       graylevel ranges from .black. (which codes
       to black ink on the paper) to .white.
       (which codes to blank paper).

     line   2:
       An (x,y) location for the bullet.

     line   3:
       Skipped.

     line 4-n:
       Locations of vertices of polygon, ended with a blank line.
     {
       read .code. .graylevel. # Read line 1
       read .x. .y.            # Read line 2
       skip                    # Skip line 3
       read columns x y        # Read a polygon
       # Adjust .graylevel. to range between 0
       # (for black ink) and 1 (for white paper),
       # then set graylevel and draw polygon.
       .graylevel. = {rpn .graylevel. \
           .black. - .white. .black. - /}
       set graylevel .graylevel.
       draw curve filled
       # Draw black bullet
       set graylevel 0
       draw symbol bullet at .x. .y.
       # Clean up local storage.
       delete .code.
       delete .graylevel.
       delete .x.
       delete .y.
     }

Temperature-Salinity Diagram
============================

Here is how you might draw an oceanographic "TS" (temperature salinity) diagram:

     # Example 13 -- TS diagram, with isopycnals
     #
     # Draw Axes
     set line width axis 0.25
     set line width 0.75
     .tic_size. = 0.1                # cm
     set symbol size 0.03
     .isopycnal_fontsize. = 8        # for isopycnal labels
     .axes_fontsize. = 10            # for axes
     set font size .axes_fontsize.
     set x margin 2
     set x size 10
     set y margin 2
     set y size 10
     .Smin. = 33.4
     .Smax. = 35.0
     .Sinc. = 0.5
     .Sincinc. = 0.1
     .thetamin. = -2.0
     .thetamax. = 11.0
     .thetainc. = 1.0
     .thetaincinc. = 1.0
     set tic size .tic_size.
     set x name "Salinity / PSU"
     set y name "Potential Temperature / $\circ$C"
     set x axis .Smin. .Smax. .Sinc. .Sincinc.
     set y axis .thetamin. .thetamax. .thetainc. .thetaincinc.
     set axes style offset
     draw axes 1
     set clip on
     .old. = ..fontsize..
     set font size .isopycnal_fontsize.
     draw isopycnal 26.00
     draw isopycnal 26.50 unlabelled
     draw isopycnal 27.00
     draw isopycnal 27.50 unlabelled
     draw isopycnal 28.00
     draw isopycnal 28.50 unlabelled
     draw isopycnal 29.00
     set clip off
     set font size .old.
     #
     # Draw the data.
     open example13.dat
     read columns x y
     draw symbol bullet
     set font size ..
     draw title "Example 13 -- TS diagram, with isopycnals"

Probability Density Function Diagram
====================================

A common application is to draw the probability density function for (x,y) data.  Gri has no builtin facility to do this, but the following example shows how to create the gridded PDF data using a call to the perl system command.  The gridded data thus generated are contoured, creating a PDF diagram.  As the comments in the program state, the first call to Perl is specific to a particular dataset, and can be ignored on first reading; it just creates the file tmp-xy.\.pid..

     # Draw prob-density-function TS diagram for Bravo data

     # This first call to perl is specific to the
     # particular (weird) dataset.  All that matters
     # is that a file of (x,y) data is created, and
     # stored in the file called `tmp-xy.\.pid.'
     system perl <<"EOF"
     #
     # Slurp in x[], y[] data
     $dir = "/users/dek/kelley/Labrador/bravo/data";
     $Sfile = "$dir/S_25db_1day";
     $Tfile = "$dir/T_25db_1day";
     open(S, "$Sfile") || die "Can't open input $Sfile";
     open(T, "$Tfile") || die "Can't open input $Tfile";
     open(ST, ">tmp-xy.\.pid.")
         || die "Can't open tmp-xy.\.pid.";
     $day = 5;
     $year = 1964;
     while(<S>) {
         @S = split;
         $_ = <T>;
         @T = split;
         if (240 < $day && $day < 360) {
             for ($i = 0; $i < $#S; $i++) { #all depths
                 print ST "$S[$i] $T[$i]\n";
             }
         }
         $day += 1;
         if ($day > 365) {
             $year++;
             $day = 0;
         }
         if ($year > 1967) { last; }
     }
     EOF

     #
     # Create 2D PDF for (x,y) data in file \infile
     # storing the results in \outfile.  X ranges
     # between the indicated limits, with the indicated
     # binsize, as does y.  The synonyms defined
     # on the next 4 lines are the only input this
     # perlscript needs; the perlscript itself is
     # quite general.  For details of what it does,
     # particularly the scaling of the PDF, see
     # the perl comments.
     \xmin = "33.5"; \xmax = "35.5"; \xinc = "0.05";
     \ymin = "-2.0"; \ymax = "11.0"; \yinc = "0.25";
     \infile = "tmp-xy.\.pid."
     \outfile = "tmp-grid.\.pid."
     system perl <<"EOF"
     #
     # Prepare 2 dimensional probability-density-function
     # dataset for contouring by Gri.  This reads (x,y)
     # data from a file called $infile (defined below)
     # and creates an output file called $outfile
     # (also defined below) containing the
     # x-grid, the y-grid, and then the grid data,
     # suitable for reading/contouring by the Gri
     # commands
     #       open tmp-grid.\.pid.
     #       read .number_of_data.
     #       read grid x
     #       read grid y
     #       read grid data
     #       draw contour
     #
     # The values in the output grid are defined so
     # that they sum to the reciprocal of the
     # product of the x binsize and y binsize (see
     # definition of $factor below).
     #
     $xmin = \xmin; $xmax = \xmax; $xinc = \xinc;
     $ymin = \ymin; $ymax = \ymax; $yinc = \yinc;
     $infile = "\infile";
     $outfile = "\outfile";
     #
     # Slurp in the x[], y[] data, storing
     # the total number of data in $n.
     open(IN,  "$infile")   || die "Can't open infile";
     open(OUT, ">$outfile") || die "Can't open outfile";
     $n = 0;
     while(<IN>) {
         ($x[$n], $y[$n]) = split;
         $n++;
     }
     #
     # Zero out matrix (stored in a linear array scanned
     # as one reads a book).
     $cols = int(1 + ($xmax - $xmin) / $xinc);
     $rows = int(1 + ($ymax - $ymin) / $yinc);
     for ($y = $ymax; $y > $ymin; $y -= $yinc) {
         for ($x = $xmin; $x < $xmax; $x += $xinc) {
             $l = int(($x - $xmin) / $xinc
                 + $cols * int(($y - $ymin) / $yinc));
             $sum[$l] = 0;
         }
     }
     #
     # Cumulate (x,y) data into the matrix
     $inside = 0;
     for ($i = 0; $i < $n; $i++) {
         if ($ymin <= $y[$i] && $y[$i] <= $ymax
             && $xmin <= $x[$i] && $x[$i] <= $xmax) {
             $l = int(($x[$i] - $xmin) / $xinc
                 + $cols * int(($y[$i] - $ymin) / $yinc));
             $sum[$l]++;
             $inside++;
         } else {
             print STDERR "($y[$i], $x[$i]) clipped\n";
         }
     }
     #
     # Print number of points (to allow renormalization
     # if the user wishes)
     print OUT "$inside\n";
     #
     # Print x grid, y grid, then grid itself
     for ($x = $xmin; $x < $xmax; $x += $xinc) {
         printf OUT "%lg\n", $x;
     }
     print OUT "\n";
     for ($y = $ymax; $y > $ymin; $y -= $yinc) {
         printf OUT "%lg\n", $y;
     }
     print OUT "\n";
     #
     # The $factor variable scales the PDF.
     $factor = 1 / $xinc / $yinc / $inside;
     for ($y = $ymax; $y > $ymin; $y -= $yinc) {
         for ($x = $xmin; $x < $xmax; $x += $xinc) {
             $l = int(($x - $xmin) / $xinc
                 + $cols * int(($y - $ymin) / $yinc));
             printf OUT "%lg ", $factor * $sum[$l];
         }
         print OUT "\n";
     }
     EOF

     # Axes
     set x margin 3
     set x margin 6
     set x name "Salinity [PSU]"
     set y name "Potential Temperature [$\circ$C]"
     set x axis 34.5 34.8 0.1
     set y axis 5 9 1
     draw axes

     # PDF
     open tmp-grid.\.pid.
     read .number_of_data.
     read grid x
     read grid y
     read grid data
     .smooth. = 0

     # Contours.  Use clipping, since the axes are
     # zooming in on part of the PDF.
     set font size 8
     set contour label position centered
     set clip postscript on
     set line width rapidograph 4x0
     draw contour 0.2 2.2 0.4 unlabelled
     set line width rapidograph 0
     draw contour 0.4 2.4 0.4
     set clip postscript off
     end if

Running-Mean Skyline Diagram
============================

Timeseries data are often cast into running means; e.g. a temperature record might be cast into monthly mean values.  The following example shows how to use a perl script to accomplish this easily, producing a graph with both the raw data (bullets) and the running mean (a skyline plot).

     `Bin with  x .min. .max. .inc. \in_file \out_file'

     Creates \out_file from \in_file.  In each of these
     files, column 1 represents x and column 2 represents
     y.  The \out_file file contains the average values
     of y in x bands of width .inc., centred at .min.,
     (.min.+.inc.), up to .max, and with missing values
     inserted in bands with no x-data in \in_file.
     Each x-band is represented in \out_file by a
     plateau in y, and adjacent bands with
     non-missing data are connnected by vertical
     lines; the effect is a skyline plot of the
     banded means.  Sample application: plot
     monthly means of a variable.
     {
         if {rpn \.words. 8 !=}
             show "ERROR: `\.proper_usage.' called without"
             show " giving all parameters"
             quit 1
         end if
         system perl <<"EOF"
         $min = \.word3.;
         $max = \.word4.;
         $inc = \.word5.;
         open(IN,   "\.word6.")
             || die "`\.proper_usage': no \\in_file";
         open(OUT, ">\.word7.")
             || die "`\.proper_usage': no \\out_file";

         $n = ($max - $min) / $inc;
         #
         # Set up bins.
         for($i = 0; $i <= $n; $i++) {
            $xx[$i] = 0;
            $yy[$i] = 0;
            $nn[$i] = 0;
         }
         while(<IN>) {
             ($x, $y) = split(' ');
             $i = int(0.5 + ($x - $min) / $inc);
             $i =      0 if $i <      0;
             $i = $n - 1 if $i > $n - 1;
             $xx[$i] += $x;
             $yy[$i] += $y;
             $nn[$i]++;
         }
         for($i = 0; $i <= $n; $i++) {
             if ($nn[$i] > 0) {
                 $xx[$i] /= $nn[$i];
                 $yy[$i] /= $nn[$i];
                 $xleft  = $min + $inc * ($i - 0.5);
                 $xright = $min + $inc * ($i + 0.5);
                 #
                 # If datum to left non-missing,
                 # just draw vertical line
                 # down to the last yy value.
                 if ($i > 0 && $nn[$i - 1] > 0) {
                     print OUT "$xleft $yy[$i - 1]\n";
                 } else {
                     print OUT "$xleft \.missingvalue.\n"
                 }
                 print OUT "$xleft  $yy[$i]\n";
                 print OUT "$xright $yy[$i]\n";
             }
         }
     EOF
     }

     # Bin into months
     Bin with x 1964 1974 {rpn 1 12 /} \
         timeseries.dat tmp.dat
     open tmp.dat
     read columns x y
     close
     draw curve                      # skyline of means
     open timeseries.dat
     read columns x y
     close
     draw symbol bullet              # data
     system rm -f tmp.dat            # clean up

Finite Element Model mesh
=========================

Finite Element Models (used in fluid mechanics) employ non-rectangular meshes, and plotting these meshes requires a few intermediate steps. Consider the common case of triangular elements.  Suppose two data files exist describing the mesh, the first, model.nodes say, consists of a description of the x-y coordinates of the nodes (vertices) of the triangles.  The second, model.elements say, consists of a description of which triplet of nodes defines each triangle in the mesh. Here, from a sample application, is a node file called model.nodes:

     1	1	1
     2	2	1
     3	1	2
     4	3	1.5
     5	2	2
     6	1.5	3

Here is the corresponding file of the elements, called model.elements

     1	1	2	3
     2	2	5	3
     3	2	4	5
     4	3	5	6

In each of these files, the first column is a reference number.  Thus, model.elements indicates that the first triangle is defined by the nodes numbered 1, 2 and 3 as defined in model.nodes.  More specifically, the triangle is defined by vertices at (x,y) locations (1,1), (2,1), and (1,2).

A Gri program, named FEM.gri, to draw the nodes is the following.

     set missing value -99.99
     # Create data using perl-script ...
     system FEM.pl model.nodes model.elements > tmp
     # ... then plot it ...
     open tmp
     read columns x y
     close
     draw curve
     # ... and, finally, clean up the temporary file
     system rm tmp

The work of interpreting the data files is done by the perlscript that follows, named FEM.pl

     #!/usr/bin/perl -w
     $missing = -99.99;              # missing value
     $node_file = $ARGV[0];
     $element_file = $ARGV[1];
     open (NODE, $node_file)
         or die "Cannot open '$node_file' file";
     open (ELEM, $element_file)
         or die "Cannot open '$element_file' file";

     # Read in node information, creating arrays
     # named $node_x[] and $node_y[]. Check that
     # the first column (the index) makes sense.
     $max_node = 1;
     while(<NODE>) {
         ($index, $node_x[$max_node], $node_y[$max_node])
             = split;
         die "Node mismatch at index=$index"
             if ($index != $max_node);
         $max_node++;
     }

     # Read in triangle elements, into arrays
     # $a[], $b[], and $c[].  Check that the
     # first column (the index) makes sense.
     $max_elem = 1;
     while(<ELEM>) {
         ($index, $a[$max_elem], $b[$max_elem], $c[$max_elem])
             = split;
         die "Element mismatch at index=$index"
             if ($index != $max_elem);
         $max_elem++;
     }

     # Print out triangles suitable for plotting in gri.
     for ($i = 1; $i < $max_elem; $i++) {
         print $node_x[$a[$i]], " ", $node_y[$a[$i]], "\n";
         print $node_x[$b[$i]], " ", $node_y[$b[$i]], "\n";
         print $node_x[$c[$i]], " ", $node_y[$c[$i]], "\n";
         # Repeat first, to close the triangle.
         print $node_x[$a[$i]], " ", $node_y[$a[$i]], "\n";
         print $missing, " ", $missing, "\n";
     }

Handling Data
=============

Handling headers
----------------

Case 1 -- known number of header lines. This is easy.  If you know that the file has, say, 10 header lines, you can just do this:

     open file
     skip 10
     read columns x y
     ...

Case 2 -- header itself indicates number of header lines. Quite often the first line of a file will indicate the number of header lines.  For example, suppose the first line contains a single number, indicating the number of header lines to follow:

     open file
     read .skip.
     skip .skip.
     read columns x y
     ...

Case 3 -- header lines marked by a textual key. Sometimes header lines are indicated by a textual key, for example, the characters HEADER at the start of the line in the file.  The easy way to skip such a header is to use a system command.  Depending on your familiarity with the operating system (here presumed to be Unix), you might choose to use Grep, Awk, or Perl.  Here are examples:

     open "grep -v '^HEADER' file |"

For more on the | mechanism, see Open.  The Grep command prints lines which do not match the indicated string (because of the -v switch), and the ^ character stands for the start of the line (Grep).  Thus all lines with the key word at the start of the line are skiped.

Case 4 -- reading and using information in header. Consider a dataset in which the first line gives the time of observation, followed by a list of observations.  This might be, for example, an indication of the data taken from a weather balloon released at a particular time from a fixed location, with the main data being air temperature as a function of elevation of the balloon.  The time indication might be, for instance, the hour number.  One might need to know the time to print a label on the diagram.  You could do that by:

     open file
     read .time.
     read columns x y
     draw curve
     sprintf \label "Time of observation is %f hour" .time.
     draw title "\label"

where the sprintf command has been used to change the numerical time indication into a synonym that can be inserted into a quoted string for drawing the title of the diagram (Sprintf).  Here the time has been assumed to be a decimal hour.  You might also have three numbers on the line, perhaps a day, an hour and a minute.  Then you could do something like

     open file
     read .d. .h. .m.
     read columns x y
     draw curve
     sprintf \label "Obs. %.0f:%.0f, day %.0f" .h. .m. .d.
     draw title "\label"

Here the %.0f code is used to ensure no numbers will be written after the decimal point.  Naturally, you could convert this to a decimal day, by e.g.

     ...
     .dday. = {rpn .day. .hour. 24 / .min. 24 / 60 /}
     sprintf \label "Decimal day is %.4f" .dday.
     ...

(Some of you might know how many minutes in a day, but I'm silly so I kept the extra mathematical step -- nothing is lost by being straightforward!)

Ignoring columns that are not of interest
-----------------------------------------

Quite often a dataset will have many columns, of which only a couple are of interest to you.  Consider for example oceanographic data which has columns storing, in order, these variables: (1) depth in water column, (2) "in situ" temperature, (3) "potential" temperature, (4) salinity, (5) conductivity, (6) density, (7) sigma-theta, (8) sound speed, and (9) oxygen concentration.  But you might only be interested in plotting a graph of salinity on the x-axis and depth on the y-axis. Here are several ways to do this:

     open file
     read columns y * * x
     draw curve

where the * is a place-keeper to indicate to skip that column. For a large number of columns, or as an aesthetic choice, you might prefer to write this a

     open file
     read columns y=1 x=4
     draw curve

Many users would just as soon not bother with this syntax, preferring instead to use system tools with which they are more familiar.  So a Gawk user might write

     open "gawk '{print($1, $4)}' file |"
     read columns y x
     draw curve

For more on the Gawk command see Awk.

Algebra on column data
----------------------

Suppose the file contains (x,y), but you wish to plot 2y times x.  You could do the doubling of y within Gri, as

     open file
     read columns x y
     y *= 2
     draw curve

or you could use a system tool, e.g. gawk, as in this example (Awk).

     open "gawk '{print($1,2*$2)}' file|"
     read columns x y
     draw curve

The latter is preferable in the sense that it is more powerful.  The reason for this is that Gri allows you to manipulate the x and y columns, using so-called RPN mathematics (rpn Mathematics), but you cannot blend the columns.  For example, you cannot easily form the ratio y/x in Gri.  (Actually, you can, by looping through your data and doing the calculation index by index, but if you knew that already you wouldn't need to be reading this section!)  Such blending is trivial in the operating system, though, as in the following Gawk example (Awk).

     open "gawk 'print {($1, $2/$1)}' file |"
     read columns x y
     draw curve

Combining columns from different files
--------------------------------------

Suppose you want to plot a column (y, say) from one file versus a second column (x) from a second data file.  The easy way is to use a system command to create a new file, for example the Unix command paste -- but of course you don't want to clutter your filesystem with such files, so you should do this withing Gri:

     open "paste file1 file2 |"
     read columns x y
     draw curve

Plotting several y-columns versus on x-column
---------------------------------------------

Sometimes you'll have a datafile with the first column being x, and the other columns being various things to plot versus x.  For example, you might have the data

     1  8 11  9
     2 22 21 20
     3 11 10  9
     4 20 15 10

in a file called test.dat.  Let's say the x-column is time, and the y-columns are the readings from three temperature sensors.  The following illustrates how you might plot these data.  If you think the new-command which starts this script is useful, just insert it in your ~/.grirc file and you can just use it without re-defining it each time.  This will give Gri a command called draw curves.

     `draw curves \xname \y1name ...'
     Draw multiple y columns versus an x column.  Assumes
     that the datafile is open, and that x is in the first
     column, with the y values in one or more following
     columns.

     The number of columns is figured out from the options,
     as is the name of the x-axis, and the labels to be
     used on each of the y curves.
     {
       # NB. the 3 below lets us skip the words 'draw'
       # and 'curves', and the name of the x-column.
       .num_of_y_columns. = {rpn wordc 3 -}
       if {rpn .num_of_y_columns. 1 >}
         show "ERROR: `draw curves' needs at least 1 y column!"
         quit
       end if

       set x name {rpn 2 wordv}
       set y name ""

       # Loop through the columns.
       .col. = 0
       while {rpn .num_of_y_columns. .col. <}
         # The x-values will be in column 1, with y-values
         # in columns 2, 3, ..., of the file.
         .ycol. = {rpn .col. 2 +}
         rewind
         read columns x=1 y=.ycol.
         # At this point, you may want to change line thickness,
         # thickness, color, dash-type, etc.  For illustration,
         # let's set dash type to the column number.
         set dash .col.
         draw curve
         draw label for last curve {rpn .col. 3 + wordv}
         .col. += 1
       end while
     }

     open test.dat
     draw curves time y1 y2 y3

List of Commands in the Gri Language
************************************

Overview of Gri Commands
========================

The Gri commands may be divided roughly into a few categories, as indicated in the following list.

  * Working with files: Commands are open, close, skip, read, and rewind.

  * Controlling parameters of the drawn material: Various set commands control values of parameters, like size of plot, linewidth, font, etc.

  * Drawing things: Various draw commands let you draw data, axes, etc.

  * Interacting with the user: The query command gets instructions from the user.  The show command displays messages to user.

  * Controlling program flow: The if statement controls optional execution of commands (If Statements).  The while statement allows loops.

  * Moving around in directories: The pwd, cd and ls commands do the usual unix things.

  * Using the operating system The system command passes instructions to the operating system; the output may be saved into a synonym by using \syn = system ....  The get env command determines the value of any unix environment variables the system has defined.  For more discussion (Operating System).

  * Statistical operations: Some very limited capabilities exist; for example, regress does linear regression.

  * Mathematical operations: Simple mathematical manipulation of column, grid, and image data is provided.  Also, wherever Gri expects a number, it will accept a reverse-polish expression; for example, set x size 10 could also be written set x size {rpn 20 2 /}.  For details (Mathematics).

Command syntax
==============

The syntax description is enclosed within angled single quotes, optional items are enclosed in square brackets, multiword items are enclosed in curly braces, and vertical bars separate different legitimate choices. For example, the documentation item for the command for drawing contours

     `draw contour \
         [.value. |  \
           {.min. .max. .inc. [.inc_unlabelled.]}] \
         [unlabelled]'

indicates that following are legal:

     draw contour                   # gri selects levels
     draw contour unlabelled        # " but unlabelled
     draw contour 10                # single contour line
     draw contour 10 unlabelled     # " but unlabelled
     draw contour 0 100 10          # contours at z=0,1,
     draw contour 0 10 1 unlabelled # " but unlabelled
     # contours at 0, 0.1, ... labelled at 0, 1
     draw contour 0 10 1 0.1

Note that items enclosed in braces must appear in their entirety; for example,

     draw contour 0 10              # WRONG; missing .inc.

which might look similar draw contour .min. .max. .inc. to you, looks like garbage to Gri.  Gri will recognize it as an attempt at the draw contour command (because the first 2 words match the syntax) but it will then get confused, spit out an error message, and quit.

List of all Gri commands
========================

Commands are listed below in the order in which they are defined in the gri.cmd file (Invoking Gri).  What you see here is similar to, but not identical to, the text of the online help.  Gri usually accepts both American and English spellings (As an example of spelling latitude, Gri accepts grey anywhere the manual says gray, and colour for color.)

assert
------

     `assert .condition. ["message"]

The condition may be a variable, a synonym, or an RPN expression.  If this condition is true (i.e. evaluates to a non-zero number), do nothing.  If the condition is false, the program will terminate with an error condition (in unix, it will terminate with a non-zero exit code).

Before termination, a message will be printed, the form of which depends on the optional "message" string.

If no "message" string is given, the the printed message will indicate the name of the command-file and the line at which the assert command was encountered.

If a "message" string is given, and if it ends in a newline ("\\n"), then this string is printed.

If a "message" string is given, and if it does not end in "\\n", then the string is printed along with an indication of the location in the command-file.

(Perl users will recognize this as being patterned on the "die" command.)

cd
--

     `cd [\pathname]'

If a pathname specified, change to that directory.  Normal unix filenames are used, as in the C-shell convention.  For example, the commands cd ~/src and cd $HOME/src are equivalent.  You may specify relative pathnames as in cd ../sister_directory.

If no \pathname directory path is specified, go to the home directory, exactly as cd ~ and cd $HOME do.

close
-----

     `close [\filename]'

If no filename is specified, close the most recently opened data-file; otherwise close the indicated file.

The convert commands
--------------------

convert columns to grid
.......................

Various forms exist:

     `convert columns to grid OPTIONS'

where the OPTIONS may be omitted or selected from this list:

     `neighbor'
     `boxcar    [.xr. .yr. [.n. .e.]]'
     `objective [.xr. .yr. [.n. .e.]]'
     `barnes    [.xr. .yr. .gamma. .iter.]'

For more discussion on the methods see Ungridded Data.

All these commands ``grid'' columnar (x,y,z) data.  That is, they fill up a grid based on some form of interpolation of the possibly randomly-spaced columnar data.  There are many methods in existence for doing this, and Gri implements several of them as alternatives.

The grid will have been defined by commands such as set x grid, set y grid, read grid x and read grid y.  As of version 2.1.9, Gri does not require a grid to have been pre-defined; it will create a regular 20 by 20 grid, spanning the range of x and y data, as a default.  This is a good starting point in many cases.

`neighbor' method
     Very fast but very limited.

`boxcar' method
     Slower but a lot better.  Still, this can produce noisy contours if the data are not densely and uniformly ditributed through domain.

`objective' method
     Somewhat slower than `boxcar', but produces better fields since the averaging function is smooth.

`barnes' method
     Somewhat slower than `objective', but only by a constant factor (that is, independent of number of data).  This produces by far the best results, since the smoothing function has variable spatial scale.  This is the default method if no method is supplied.

All except the neighbor method may take optional arguments to define the x and y scales of the smoothing function (called .xr. and .yr.).  (The barnes method has two other optional arguments -- see below.)  If you do not supply these arguments, Gri will make a reasonable choice and inform you of its decision.  Many users find that it is best to convert columns to grid with no additional parameters as a first step, to get advice on values to use for the optional parameters.

The default .xr. and .yr. are calculated by determining the span in x and in y directions, and dividing each by the square root of the number of data points.  These numbers are then multiplied by the square root of 2.  The method is as proposed by S. E. Koch and M. DesJardins and P. J. Kocin, 1983.  ``An interactive Barnes objective map anlaysis scheme for use with satellite and conventional data,'', J. Climate Appl.  Met., vol 22, p. 1487-1503.

If .xr. and .yr. were supplied but negative, then Gri interprets this as an instruction to modify the default values, described in last paragraph, by multiplying by the absolute values of the negative numbers given, instead of muliplying by square root of 2.

If the chatty option is turned on then Gri will print out the values of (dx,dy) that it has calculated; this gives you some guidance for supplying your own values of (.xr.,.yr.) if you choose to supply them yourself.  It is also a good idea to let these parameters be a guide for your grid spacing; for example, Koch et al., 1983, suggest using grid spacing of 0.3 to 0.5 times (dx,dy).

And now, the details ...

  * ``Neighbor'' method The convert columns to grid neighbor method is useful for (x,y,z) data which are already gridded (i.e., for which x and y take only values which lie on the grid), or nearly gridded.  The (x,y,z) data are scanned from start to finish. For each data point, the nearest grid point is found.  Nearness is measured as Cartesian distance, with scale factor given by the distance between the first and second grid points.  In other words, distance is given by D=sqrt(dx*dx+dy*dy) where dx is ratio of distance from data point to nearest grid point, in x-units, divided by the difference between the first two elements of the x-grid, and dy is similarly defined.  Once the grid point nearest the data point is determined, Gri adds the z-value to a list of possible values to store in the grid.  Once the entire data set has been scanned, Gri then goes back to each grid point, and chooses the z-value of the data point that was nearest to the grid point -- that is, it stores the z value of the (x,y,z) data triplet which has minimal D value.  Note that this scheme is independent of the order of the data within the columns.

     The neighbor method is useful when the data are already pre-gridded, meaning that the (x,y,z) triplets have x and y values which are already aligned with the grid.  Computational cost: For P data points, X x-grid points, and Y y-grid points, the method calculation cost is proportional to P*[log2(X)+log2(Y)] where log2 is logarithm base 2. As discussed below, this is often several orders of magnitude lower than the other methods of gridding.

  * ``Objective'' method In the objective method, a smoothing technique known as objective mapping is applied.  It is essentially a variable-size smoothing filter of approximately Gaussian shape (it is method ``two'' of Levy and Brown [1986 J. Geophysical Res. vol 91, p 5153-5158]) The parameters .xr. and .yr. give the width of the filter.

     With the optional additional parameters .n. and .e. are specified, then grid values will be assigned the missing value if there are fewer than .n. (x,y,f) data in the neighborhood of the gridpoint, even after enlarging the neighborhood by widening and heightening by root(2) up to .e. times.  (The enlargement is only done if fewer than .n. points are found.)  If these parameters are not specified in the command, then values .n.=5 and .e.=1 are assumed.  The special case where .e. is negative tells Gri to always fill in each grid point, by extending the neighborhood to enclose the entire dataset if necessary.

     Computational cost: For P data points, X x-grid points, and Y y-grid points, the method calculation cost is proportional to P*X*Y.  Given that X and Y are determined by the requirement for smoothness of contours and the size of the graph, they are more or less fixed for all applications.  They are often in the range of 20 or so -- on 10 cm wide graph, this yields a contour footprint of 1/2 cm, which is often small enough to yield smooth contours.  Therefore, the computational cost scales linearly with the number of data points.  Compared to the ``neighborhood'' method, this is more costly by a factor of X*Y/log_2(X)/log_2(Y) which is normally in the range from 20 to 50.

  * ``Boxcar'' method In the boxcar method, the grid points are derived from simple averages calculated in rectangles .xr. wide and .yr. tall, centred on the gridpoints.  The .n. and .e. parameters have similar meanings as in the ``objective'' method.

     Computational cost: Roughly same as objective method described above.

  * ``Barnes'' method This is the default scheme.

     The Barnes algorithm is applied.  If no parameters are specified, .xr. and .yr. are determined as above, with .gamma. set to 0.5, and .iter. set to 2 so that two iterations are done. On successive iterations, the smoothing lengthscales .xr and .yr are each reduced by multiplying by the square root of .gamma..  Smaller .gamma. values yield better resolution of small-scale features on successive iterations.  Koch et al., 1983, recommend using a .gamma. value in the range 0.2 to 1, with two iterations.

     Provided that all the grid points are close enough to at least some column data, the entire grid is filled.  But if .xr. and .yr. are too small, the weighting function can fall to zero, since it is exponential in the sum of the squares of the x-distance/.xr. and the y-distance/.yr.; in that case missing values result at those grid points.  On a 32 bit computer, the weighting function will fall to zero when x-distance/.xr.  and y-distance/.yr.  are less than about 15 to 20.

     If weights have been read in (Read Columns), then these values are applied in addition to the distance-based weighting.  (The normalization means that weights for two data points of e.g. 1 and 2 will yield the same result as if the weights had been given as 10 and 20.)

     The computational cost at each iteration scales as P*X*Y).  This is comparable to that of the ``objective'' and ``boxcar'' methods. Since normally two iterations are done, ``barnes'' is about double the cost of these methods.  (Note: versions prior to 2.1.8 were much slower for large datasets, being proportional to P*P.)

     References: (1) Section 3.6 in Roger Daley, 1991, ``Atmospheric data analysis,'' Cambridge Press, New York. (2) S. E. Koch and M. DesJardins and P. J. Kocin, 1983.  ``An interactive Barnes objective map anlaysis scheme for use with satellite and conventional data,'', J. Climate Appl. Met., vol 22, p. 1487-1503.

The Barnes algorithm is as follows:

The gridded field is estimated iteratively.  Successive iterations retain largescale features from previous iterations, while adding details at smaller scales.

The first estimate of the gridded field, here denoted G_(ij)^0 (the superscript indicating the order of the iteration) is given by a weighted sum of the input data, with z_k denoting the k-th z value.

                  sum_1^n W_(ijk)^0 z_k
     G_(ij)^(0) = ----------------------
                    sum_1^n W_(ijk)0

where the notation sum_1^n means to sum the elements for the k index ranging from 1 to n.

The weights W_(ijk)^0 are defined in terms of a Guassian function decaying with distance from observation point to grid point:

                    (   (x_k - X_i)^2       (y_k - Y_j)^2  )
     W_(ijk)^0 = exp(-  --------------  -  --------------- )
                    (      L_x^2                L_y^2      )

Here L_x and L_y are lengths which define the smallest (x,y) scales over which the gridded field will have significant variations (for details of the spectral response see Koch et al. 1983).

Note: if the user has supplied weights then these are applied in addition to the distance-based weights.  That is, w_i W_(ijk) is used instead of W_(ijk).

The second iteration derives a grid G_(ij)^1 in terms of the first grid G_(ij)^0 and ``analysis values'' f_k^0 calculated at the (x_k,y_k) using a formula analogous to that above.  (Interpolation based on the first estimate of the grid G_(ij)^0 can also be used to calculate f_k^0, with equivalent results for a grid of sufficiently fine mesh.)  In this iteration, however, the weighted average is based on the difference between the data and the gridded field, so that no further adjustment of the gridded field is done in regions where it is already close to through the observed values.  The second estimate of the gridded field is given by

                            sum_1^n W_(ijk)^1 (f_k - f_k^0)
     G_(ij)^1 = G_(ij)^0 +  -------------------------------
                                   sum_1^n W_(ijk)^1

where the weights w_{ik,1} are defined by analogy with W_{ik}^0 except that L_x and L_y are replaced by gamma^{1/2}L_x and gamma^{1/2}L_y.  The nondimensional parameter gamma (0<gamma<1) controls the degree to which the focus is improved on the second iteration.  Just as the weighting function forced the gridded field to be smooth over scales smaller than L_x and L_y on the first iteration, so it forces the second estimate of the gridded field to be smooth over the smaller scales gamma^{1/2}L_x and gamma^{1/2}L_y.

The first iteration yields a gridded field which represents the observations over scales larger than (L_x,L_y), while successive iterations fill in details at smaller scales, without greatly modifying the larger scale field.

In principle, the iterative process may be continued an arbitrary number of times, each time reducing the scale of variation in the gridded field by the factor gamma^{1/2}.  Koch et al. 1983 suggest that there is little utility in performing more than two iterations, providing an appropriate choice of the focussing parameter gamma has been made. Thus the gridding procedure defines a gridded field based on three tunable parameters: (L_x,L_y,gamma).

convert columns to spline
.........................

     `convert columns to spline \
         [.gamma.] \
         [.xmin. .xmax. .xinc.]'

Fit a normal or taut interpolating spline, y=y(x), through the (x,y) data.  Then subsample this spline to get a new set of (x,y) data.  If the spline x-values, .xmin., etc, are not specified, the spline ranges from the smallest x-value with legitimate data to the largest one, with 200 steps in between.

The parameter .gamma. determines the type of spline used.  If .gamma. is not specified, or is given as zero, a standard interpolating spline is used.  A knot appears at each x location, with cubic polynomials spanning the space between the knots.  If .gamma. lies between 0 and 6, a taut spline is used; this tends to have fewer wiggles than a normal spline.  If .gamma.  lies in the range 0 to 3, a taut spline is used, with the possible insertion of knots between interior x pairs.  The value 2.5 is used commonly.  If .gamma. lies in the range 3 to 6, extra knots are permitted in the x pairs at the ends of the domain.  A value of 5.5 is used commonly.

Reference Chapter 16 of Carl de Boar, 1987. ``A Practical Guide to Splines'' Springer-Verlag.

     read columns x y  # function is y=x^2
     0 0
     1 1
     2 4
     3 9
     4 16

     set symbol size 0.2
     draw symbol bullet
     convert columns to spline
     draw curve

convert grid to columns
.......................

     `convert grid to columns'

Create column data from grid data.  Each non-missing gridpoint is translated into a single (x,y,z) triplet.  If column data already exist, then they are first erased.  This command is useful in changing the grid configuration, perhaps from a non-uniform grid to a uniform grid.  In the following example, a new grid with x=(0, 0.05, 0.1, ..., 0.1) and y=(10, 11, ..., 20) is created.  The default gridding method (convert columns to grid) is used here, but of course one is free to adjust the method as usual.

     # ... read/create grid
     convert grid to columns
     delete grid
     set x grid  0  1 0.05
     set y grid 10 20 1
     convert columns to grid

convert grid to image
.....................

     `convert grid to image [directly] [size .width. .height.] \
         [box .xleft. .ybottom. .xright. .ytop.]'

With no options specified, convert grid to a 128x128 image, using an image range as previously set by set image range, and using interpolation (see below).

With the directly option, no interpolation is used; each grid point is used to calculate the colour of a single image pixel.  Since images are always uniform in Gri, this will only work if the grid is also uniform, i.e. there must be a constant distance between columns in the grid, and the same for the rows.  This method is useful for fine-grained grids, especially if they contain isolated points (e.g. a numerical model might have a trace of points representing a river).

With the size options .width. and .height. specified, they set the number of rectangular patches in the image. Interpolation is used.

With the box options specified, they set the bounding box for the image.  If box is not given, the image spans the same bounding box as the grid as set by set x grid and set y grid.  Again, interpolation is used in this form.

Normally, missing values in the grid become white in the image, but this can be changed using the set image missing value color to... command.

Interpolation method: The interpolation scheme is the same used for contouring.  Image points that lie outside the grid domain are considered missing.  For points within the grid, the first step is to locate the patch of the grid upon which the pixel lies.  Then the 4 neighboring grid points are examined, and one of the following cases holds.

 1. If 3 or more of them are missing, the pixel is considered missing.

 2. If just one of the neighboring grid points is missing, then the image pixel value is determined by bilinear interpolation on the remaining 3 non-missing grid points.  (This amounts to fitting a plane to three measurements of height.)

 3. If all 4 of the grid points are non-missing, then the rectangle defined by the grid patch is subdivided into four triangles.  The triangles are defined by the two diagonal lines joining opposite corners of the rectangle.  An ``image point'' is constructed at the center of the grid patch, with f(x,y) value taken to be the average of the values of the four neighbors.  This value is taken to be the value at the common vertex of the four triangles, and then bilinear interpolation is used to calculate the image pixel value.

convert image to grid
.....................

     `convert image to grid'

Convert image to grid, using current graylevel/colorlevel mapping.  For example, if one had a linear mapping of pixel values 0->255 into the user values 10->20, as in

     set image range 10 20
     set image grayscale black 10 white 20

then the output grid will be of value 10 where the pixel value is 0, etc.  If the image is in color, the grid values will represent the result of mapping the colors to grayscale in the standard way (Foley and VanDam, 1984). [BUG: as of 1.063, the colorscale is ignored completely, and I'm not sure what happens.] The image data are interpolated onto the grid using a nearest-neighbor substitution.  This command insists that the image x/y grids have already been defined.

The create commands
-------------------

create columns from function
............................

     `create columns from function'

Plot a function of x which is defined in synonym \function.

     ENVIRONMENT
     \function = function to plot.
     \xmin     = minimum x value
     \xmax     = maximum x value
     \xinc     = increment in x values

     EXAMPLE
     \function = "cos(x)"
     \xmin     = "0"
     \xmax     = "2 * 3.14"
     \xinc     = "0.1"
     create columns from function
     draw curve

NOTE: This only works on machines which have the awk command available at the commandline.  This means most unix machines and some vax machines.

create image grayscale
......................

     `create image grayscale banded .band.'

Make a banded grayscale with in units of .band. pixel values each. Thus, pixel values 0 to (.band. - 1) on the image will map to 0, while values from .band. to (2 * .band. - 1) will map to .band., etc.  For example, .band. = 2 gives grayscale = (0 0 2 2 4 4 6 6 ... 252 252 254 254).

debug
-----

     `debug [.n.]|[clipped values in draw commands]|off'

With no optional parameters, sets the value of ..debug.. to 1. (Normally, ..debug.. is 0.)  You may use ..debug.. in if statements, etc.  Note that ..debug.. is also set to 1 when gri is invoked with the commandline switch -d.

With .n. specified, ..debug.. is set to .n.; a value of zero for .n. turns debugging off, while 1 turns it on. Higher values may be used for deeper debugging, if you choose:

     if {rpn ..debug.. 2 <}
       # Code to do if ..debug.. is greater than 2.
     end if

Note that you can assign to ..debug.. as you can to any other variable; debug .n. is equivalent to ..debug.. = .n..

With the clipped option, Gri prints any clipped data encountered during any draw ... commands, EXCEPT in the case of postscript clipping, where no check is possible.  (Note that ..debug.. is not affected.)

All these forms of debugging are cancelled by debug off.

delete
------

     `delete .variable.|\synonym [.variable.|\synonym [...]]'
     `delete columns [where missing]'
     `delete columns [randomly .fraction.]'
     `delete grid'
     `delete [x|y] scale'

Delete some item or characteristic.

  * delete .variable. Delete definition of variable .variable., making it undefined. Any number of variables or synonyms may be specified on one line.

  * delete \synonym Delete definition of synonym \synonym, making it undefined.  Any number of variables or synonyms may be specified on one line.

  * delete \@alias Delete the item named by the alias (Alias Synonyms).

  * delete with an & item Delete the item in the calling program.

  * delete columns Delete column data.

  * delete columns where missing Completely delete all column data for which any one of x, y, etc is missing.

  * delete columns randomly .fraction. Randomly select fraction .fraction.  of the non-missing column data, and designate them as being missing.

  * delete grid Delete grid data.

  * delete scale Delete scales for both x and y, so next read columns will set it.

  * delete x scale Delete scales for x, so next read columns will set it.

  * delete y scale Delete scales for y, so next read columns will set it.

differentiate
-------------

     `differentiate {x|y wrt index|y|x} | {grid wrt x|y}'

Differentiate column data or grid data.  Only the x and y columns may be differentiated.  They may be differentiated either with respect to (``wrt'') the index (forming a first difference) or with respect to the other column.  The derivative is done with the backwards-difference algorithm.  Grid data may differentiated with respect to x direction or y direction.  Grid differentiation is done with a centred difference, with endpoints being assigned the derivative of the neighboring interior point (so that the second derivative is zero at the edges of the grid).

The draw commands
-----------------

Draw commands do actual drawing on the page.  You can draw axes, lineplots, symbols, contours, images, and text.

NOTE Gri likes drawings to have axes, so if a draw command is executed before any axes have been drawn, Gri will draw axes after it draws the item.  (You can get drawings without axes by preceding any other draw commands with the command draw axes none.) Many users have been surprised by the results of this rule.  For example, if you do set graylevel 0.5 before draw curve, you'll find that the axes are drawn in gray also.  To avoid this, make sure to do draw axes before you modify the graylevel.)

The draw arc command
....................

     `draw arc [filled] .xc_cm. .yc_cm. .r_cm. .angle_1. .angle_2.'

Draw an "arc", that is, a portion of a circle.  The center of the circle is at the coordinate (.xc_cm., .yc_cm.), and the circle radius is .r_cm., all three quantities being in cm on the page, not in user-units.  The arc starts at angle .angle_1., measured in degrees counterclockwise from a horizontal line, and extends to angle .angle_2., in the same units.

If the keyword filled is present, the arc is filled with the current color.  Otherwise it is drawn with the current "curve" linewidth Set Line Width.

draw arrow
..........

     draw arrow from .x0. .y0. to .x1. .y1. [cm]

With no optional parameters, draw an arrow from (.x0., .y0.) to (.x1., .y1.), where coordinates are in user units.  The arrow head will be at (.x1., .y1.), and its size is as set by most recent call to set arrow size.  With the cm keyword present, the coordinates are in centimetres on the page.  NOTE: This will not cause auto-drawing of axes.

draw arrows
...........

     `draw arrows'

Draw a vector field consisting of arrows emanating from the coordinates stored in the (x, y) columns.  The lengths and orientations of the arrows are stored in the (u, v) columns, and the scale for the (u,v) columns is set by set u scale and set v scale.  See also (1) To set arrow size, use set arrow size.  (2) To get a single arrow, use draw arrow.

draw axes if needed
...................

     `draw axes if needed'

Draw axes frame if required.  Used within gri commands that auto-draw axes. NOTE: this should only be done by developers.

draw axes
.........

     `draw axes [.style.|frame|none]'

With no style (.style.) specified, draw x-y axes frame labelled at left and bottom. The value of .style. determines the style of axes:

  * .style. = 0 Draw x-y axes frame labelled at left and bottom.  Since this is the default, it's best to leave it out altogether to make your code easier to understand.

  * .style. = 1 Draw axes without tics at top and right

  * .style. = 2 Draw axes frame with no tics or labels; same as draw axes frame

With the keyword frame specified, draw axes frame with no tics or labels (just like .style. = 2, but preferable because it makes for code that is easier to read and understand).

With the keyword none specified, prevent Gri from automatically drawing axes when drawing curves.

Note: set axes style can also be used to set axes properties, and then simply using draw axes, or letting axes be auto-drawn, will result in the desired effect (Set Axes Style).  However, if the draw axes command explicitly asks for a particular style, then it over-rides the style set by Set Axes Style.

draw border box
...............

     `draw border box .xleft. .ybottom. .xright. .ytop. \
         .width_cm. .brightness.'

Draw gray box, as decoration or alignment key for pastup. The box, with outer lower left corner at (.xleft., .ybottom.) and outer upper right corner at (.xright., .ytop.) -- both coordinates being in centimetres on the page -- is drawn with thickness .width_cm. and with graylevel .brightness. (0 for black; 1 for white).  The gray line is drawn inside the box.  After drawing the gray line, a thin black line is drawn along the outside edge.

If the geometry is not specified with .xleft. and the other parameters, then a reasonable margin is used around the present axes area, and the defaults (.border. = 0.2, .brightness. = 0.75) are used.

NOTE: This command does not cause auto-drawing of axes.

draw box
........

     `draw box filled .xleft. .ybottom. .xright. .ytop. [cm|pt]'

Draw filled box spanning indicated range, with lower-left corner at (.xleft., .ybottom.) and upper-right corner at (.xright., .ytop.).  The corners are specified in user coordinates, unless the optional cm or pt keyword is present, in which case they are in centimetres or points on the page. An error will result if you specify user coordinates but they aren't defined yet.

No checking is done on the rectangle; for example, there is no requirement that .xleft. be to the left of .xright. in your coordinate system.

NOTE: if the box is specified in user units, this command will cause auto-drawing of axes, but not if the box is specified in cm or pt units

     `draw box .xleft. .ybottom. .xright. .ytop. [cm|pt]'

Draw box spanning indicated range, with lower-left corner at (.xleft., .ybottom.) and upper-right corner at (.xright., .ytop.).

The corners are specified in user coordinates, unless the optional cm or pt keyword is present, in which case they are in centimetres or points on the page.  An error will result if you specify user coordinates but they aren't defined yet.

No checking is done on the rectangle; for example, there is no requirement that .xleft. be to the left of .xright. in your coordinate system.

draw circle
...........

     draw circle with radius .r_cm. at .x_cm. .y_cm.

Draw circle of specified radius (in cm) at the specified location (in cm on the page).

draw contour
............

     `draw contour [{.value. \
       [unlabelled | {labelled "\label"}]} \
       | {.min. .max. .inc. \
         [.inc_unlabelled.] [unlabelled]}]'

This command draws contours based on the "grid" data previously read in by a read grid data command or created by gridding column data with a create grid from columns command.  If the grid data don't exist, or if the x and y locations of the grid points do not exist (see set x grid, set y grid, etc), Gri will complain.

With no optional parameters, draw labelled contours at an interval that is picked automatically based on the range of the data.

With a single numerical value (.value.), draw the indicated contour.  With the addition of labelled "\label", put the indicated label instead of a numeric label.  This can be useful for using scientific notation instead of computer notation for exponents, e.g.  draw contour 1e-5 labelled "10$^{-5}$".

With (.min., .max. and .inc.) given, draw contours for z(x,y) = .min., z(x,y) = .min. + .inc., z(x,y) = .min. + 2*.inc., ..., z(x,y) = .max.

With the additional value .inc_unlabelled. specified, extra unlabelled contours are drawn at this finer interval.

With the optional parameter unlabelled at the end of any form of this command (except the labelled "\label" variation, of course), Gri will not label the contour(s).

Hint: It can be effective to draw contours at a certain interval with labels, and a thicker pen, e.g.

     set line width rapidograph 3x0
     draw contour -2 5 1 0.25
     set line width rapidograph 1
     draw contour -2 5 1

Interpolation method: The interpolation scheme is the same used for converting grid-values to image values (Convert Grid To Image).

See also set contour labels

draw curve
..........

Several forms exist.

     `draw curve'

Draws a curve connecting the points (x,y), which have been read in by a command like read columns x y.  Line segments are drawn between all (x,y) points, except: (1) no line segments are drawn to any missing data (see set missing value), and (2) if clipping is turned on (see set clip on), no line segments are drawn outside the clipping region.  See also draw curve overlying

     `draw curve overlying'

Like draw curve, except that before drawing, the area underneath the curve (+/- one linewidth) is whited out.  This clarifies graphs where curves overlie other curves or the axes. See also draw curve.

     `draw curve filled [to {.y. y}|{.x. x}]'

The form draw curve filled ... draws filled curves.  If the to .value. is not specified, fill the region defined by the x-y points using the current paint colour (see set graylevel).  To complete the shape, an extra line is drawn between the first and last points.

The form draw curve filled to .y. y fills the region between y(x) and y = .y.; do not connect the first and last points as in the case where to .yvalue. is not specified.

The form draw curve filled to .x. x fills the region between x(y) and x = .x.

draw essay
..........

     `draw essay "text"|reset'

Draw indicated text on the page.  Succeeding calls draw text further and further down the page, starting at the top.

The current font size is used; to alter this, use set font size before draw essay.

When reset is present instead of text, the drawing position is reset to the top of the page.  Use this after a new page command to ensure that the next text lines will appear at the top of the page as expected.  EXAMPLE:

     set font size 2 cm
     draw essay "Line 1, at top of page"
     draw essay "Line 2, below top line"

draw gri logo
.............

     `draw gri logo .x_cm. .y_cm. .height_cm. .style. \fgcolor \bgcolor'

Draw a Gri logo at given location with given style and colors.  The lower-left corner of the logo will be .x_cm. centimeters from the left-hand side of the page and .y_cm. centimeters from the bottom of the page.  The logo will be .height_cm. centimeters tall.  The textual parameters \fgcolor and \bgcolor give the foreground and background colors, respectively, and these are used in styles as noted in the table below

     .style.    style
     =======    ===================
        0       stroke curve
        1       fill with color \fgcolor, no background
        2       fill with color \fgcolor it in tight box of color \bgcolor
        3       as 2 but in square box
        4       draw in \fgcolor on top of shifted copy in \bgcolor

An example is given below

     draw gri logo 1 1 3 4 blue green

draw grid
.........

     `draw grid'

Draw plus-signs at locations where grid data are non-missing.

draw image histogram
....................

     `draw image histogram \
       [box .llx_cm. .lly_cm. .urx_cm. .ury_cm.]'

With no optional parameters, draw histogram of all unmasked parts of the image, placing it above the current top of the plot.

When the box options are present, they specify the box (in centimetre coordinates on the page) in which the histogram plot is to be done.

draw image palette
..................

     `draw image palette
        [axisleft|axisright|axistop|axisbottom]
        [left .left. right .right. [increment .inc.]]
        [box .xleft_cm. .ybottom_cm. .xright_cm. .ytop_cm.]'

With no optional parameters, draw palette for image, placed above the current top showing values ranging from .min_value. to .max_value. as given in set image range.

Optional keywords (axisleft, etc) control the orientation of the palette, the default being axisbottom.

The optional parameters .left. and .right. may be used to specify the range to be drawn in the palette.  If the additional optional parameter .inc. is present, it specifies the interval between tics on the scale; if not present, the tics are at increments of 2 * (.right. - .left.).  (If .inc.  has the wrong sign, it will be corrected without warning.)

When the optional box parameters are present, they prescribe the bounding box to contain the palette.  The units are centimetres on the page.  If these parameters are not present, the box will be drawn above the image plot.

Hint It is a good idea to make the palette range .left. to .right. extend a little beyond the range of full white and full black, since otherwise neither pure white nor pure black will appear in the colorbar.  For example

     set image grayscale black 0 white 1 increment 0.1
     draw image palette left -0.1 right 1.1 increment 0.1

Hint Continuous-tone images with superimposed contours are often effective.  To get the contour lines drawn on the image palette, do something like this

     draw image
     .left.   = 0
     .right.  = 9
     .inc.    = 1
     .space.  = 3
     .height. = 1
     draw image palette left .left. \
       right .right. \
       increment .inc. \
       box \
         ..xmargin.. \
         {rpn ..ymargin.. ..ysize.. + .space. + } \
         {rpn ..xmargin.. ..xsize.. +} \
         {rpn ..ymargin.. ..ysize.. + .space. + .height. + }
     draw contour .left. .right. .inc. unlabelled

     .c. = .left.
     while {rpn .right. .c. <= }
       .c_cm. = {rpn .c. .left. - \
        .right. .left. - / \
         ..xsize.. * ..xmargin.. +}
       draw line from \
         .c_cm. \
         {rpn ..ymargin.. ..ysize.. + .space. + }\
         to \
         .c_cm. \
         {rpn ..ymargin.. ..ysize.. + .space. + .height. +} \
         cm
       .c. += 1
     end while

draw image
..........

     `draw image'

Draw black/white image made by convert grid to image or by read image.

draw isopycnal
..............

     `draw isopycnal \
        [unlabelled] .density. [.P_sigma. [.P_theta.]]'

Draw isopycnal curve for a temperature-salinity diagram.  This curve is the locus of temperature and salinity values which yield seawater of the indicated density, at the indicated pressure.  The UNESCO equation of state is used.

For the results to make sense, the x-axis should be salinity and the y-axis should be either in-situ temperature or potential temperature.

The .density. unit is kg/m^3.  If the supplied value exceeds 100 then it will be taken to indicate the actual density; otherwise it will be taken to indicate density minus 1000 kg/m^3.  (The deciding value of 100 kg/m^3 was chosen since water never has this density; the more intuitive value of 1000 kg/m^3 would be inappropriate since water can have that density at some temperatures.)  Thus, 1020 and 20 each correspond to an actual density of 1020 kg/m^3.

The reference pressure for density, .P_sigma., is in decibars (roughly corresponding to meters of water depth).  If no value is supplied, a pressure of 0 dbar (i.e. atmospheric pressure) is used.

The reference pressure for theta, .P_theta., is in decibars, and defaults to zero (i.e. atmospheric pressure) if not supplied.  This option is used if the y-axis is potential temperature referenced to a pressure other than the surface.  Normally the potential temperature is, however, referenced to the surface, so that specifying a value for .P_theta. is uncommon.

By default, labels will be drawn on the isopycnal curve; this may be prevented by supplying the keyword unlabelled.  If labels are drawn, they will be of order 1000, or of order 10 to 30, according to the value of .density. supplied (see above).  The label format defaults to "%g" in the C-language format notation, and may be controlled by set contour format.  The label position may be controlled by set contour label position command (bug: only non-centered style works).  Setting label position is useful if labels collide with data points.  Labels are drawn in the whiteunder mode, so they can white-out data below.  For this reason it is common to draw data points after drawing isopycnals.

If the y-axis is in-situ temperature, the command should be called without specifying .P_sigma., or, equivalently, with .P_sigma. = 0.  That is, the resultant curve will correspond to the (S,T) solution to the equation

     .density. = RHO(S, T, 0)

where RHO=RHO(S,T,p) is the UNESCO equation of state for seawater.  This is a curve of constant sigma_T.

If the y-axis is potential temperature referenced to the surface, .P_theta. should not be specified, or should be specified to be zero.  The resultant curve corresponds to a constant value of potential density referenced to pressure .P_sigma., i.e. the (S,theta) solution to the equation

     .density. = RHO(S, theta, .P_sigma.)

For example, with .P_sigma.=0 (the default), the result is a curve of constant sigma_theta.

If the y-axis is potential temperature referenced to some pressure other than that at the surface, .P_theta. should be supplied.  The resultant curve will be the (S,theta) solution to the equation

     .density. = RHO(S, T', .P_sigma.)

where

     T'=THETA(S, theta, .P_theta., .P_sigma.)

where THETA=THETA(S,T,P,Pref) is the UNESCO formula for potential temperature of a water-parcel moved to a reference pressure of Pref.  Note that theta, potential temperature referenced to pressure .P_theta., is the variable assumed to exist on the y-axis.

draw isospice
.............

     `draw isospice .spice. [unlabelled]'

Draw an iso-spice line for a "TS" diagram, using (S, T) data stored in files in a subdirectory named iso-spice0 in a directory named by the unix environment variable GRI_EOS_DIR.  You must set this environment variable yourself, in the normal unix way.  If GRI_EOS_DIR is not defined, Gri looks in the directory /data/po/ocean/EOS/iso0; of course, this will work only for people on the same machine as the author.

Only certain iso-spice lines are stored in these files, so only certain values of .spice. are allowed.  They are 21.75, 22.00, 22.25, ..., 30.75.  You must supply .density. in exactly this format (with 2 decimal places), or else Gri will not find the appropriate TS file, and will give a "can't open file" error.  NB: isopycnals ranging from about 23.00 to 26.00 cross a TS diagram spanning 34<S<36 and 0<T<10.

The line is labelled at the right with the density value, unless the unlabelled option is given.

Clipping should be on when drawing iso-spice lines.  A warning will be given if the isospice line does not intersect the clipping region.

EXAMPLE

     set clip on
     draw isospice line 27.00
     draw isospice line 27.50 unlabelled

draw label
..........

     `draw label boxed "string" at .xleft. .ybottom. [cm]'

Draw boxed label for plot, located with lower-left corner at indicated (x,y) position (specified in user units or in cm on the page).  The current font size and pen color are used.  The geometry derives from the current font size, with the label being centered within the box.

draw label whiteunder
.....................

     `draw label whiteunder "\string" at .xleft. .ybottom. [cm]'

Draw label for plot, located with lower-left corner at indicated (x,y) position (specified in user units or in cm on the page).  Whiteout is used to clean up the area under the label.  BUGS: Cannot handle angled text; doesn't check for super/subscripts.

draw label for last curve
.........................

     `draw label for last curve "label"'

Draw a label for the last curve drawn, using the ..xlast.. and ..ylast.. built-in variables.

draw label
..........

     `draw label "\string" [centered|rightjustified] \
         at .x. .y. [cm|pt] \
         [rotated .deg.]'

With no optional parameters, draw string at given location in USER units.

With the cm or pt keyword is present, the location is in centimetres or points on the page.

With the rotated keyword present, the angle in degrees from the horizontal, measured positive in the counterclockwise direction, is given.

With the keyword centered present, the text is centered at the given location; similarly the keyword rightjustified makes the text end at the given location.

draw line from ... to
.....................

     `draw line from .x0. .y0. to .x1. .y1. [cm|pt]'

With no optional parameters, draw a line from (.x0., .y0.)  to (.x1., .y1.), where coordinates are in user units.  With the cm or pt keyword present, the coordinates are in centimetres or points on the page.  NOTE: This will not cause auto-drawing of axes.

draw line legend
................

     `draw line legend "label" at .x. .y. [cm] [length .cm.]'

Draw a legend identifying the current line type with the given label.  A short horizontal line is drawn starting at the location (`.x.', .y.), which may be specified in centimetres or, the default, in user coordinates.  The line length is normally 1 cm, but this length can be set by the last option.  The indicated label string is drawn 0.25 cm to the right of the line.

See also draw symbol legend ....

EXAMPLE (of keeping track of the desired location for the legend)

     .offset. = 1                    # cm to offset legends
     # ... get salinity data
     set line width 0.25
     draw curve
     draw line legend "Salinity" at .x. .y.
     # ... get temperature data
     set line width 1.0
     set dash 0.45 0.05
     draw curve
     .y. += .offset.
     draw line legend "Temperature" at .x. .y.

draw lines
..........

     `draw lines {vertically .left. .right. .inc.} | \
         {horizontally .bottom. .top. .inc.}'

Draw several lines, either vertically or horizontally.  This can be useful in drawing gridlines for axes, etc.  The following example shows how to draw thin gray lines extending from the labelled tics on the x axis (ie, at 0, 0.1, 0.2, ... 1):

     set x axis 0 1 0.1 0.05
     set y axis 10 20 10
     draw axes
     set graylevel 0.75
     set line width 0.5
     draw lines vertically 0 1 0.1
     set graylevel 0

draw patches
............

     `draw patches .width. .height. [cm]'

With the optional cm keyword not present, draw column data z(x,y) as gray patches according to the grayscale as set by most recent set image grayscale.  The patches are aligned along the horizontal, and have the indicated size in user units.

With the optional keyword cm is present, the patch size is specified in centimetres.

draw polygon
............

     `draw polygon [filled] .x0. .y0. .x1. .y1. [other pairs] [user|cm|pt]'

Draw a polygon connecting the indicated points, specified in user units.  The last point is joined to the first by a line segment.  At least two points must be specified.  If the filled keyword is present, the polygon is filled with the current pen color.  If no unit is given, user units are used.

draw regression line
....................

     `draw regression line [clipped]'

Fit and draw a regression line to column data, of the form y = ..coeff0.. + ..coeff1.. * x, exporting ..coeff0.., ..coeff0_sig.., ..coeff1..  and ..coeff1_sig..  as global variables (Regress).

Normally, the line is not clipped to the axes frame, but it will be if the keyword clipped is given.

HINT: to label the plot you might do the following:

     sprintf \label "y = %f + %f * x. R$^2$=%f" \
       ..coeff0.. ..coeff1.. ..R2..
     draw title "The linear fit is \label"

draw symbol ... at
..................

     `draw symbol .code.|\name at .x. .y. [cm|pt]'

Draw a symbol at given (single) location.  The location is normally in user coordinates; it will be in centimetres on the page if the optional cm or pt keyword is given.

With the optional numerical/name code specified, then the symbol of that number or name is drawn at each (x,y) datum, whether or not a z-column exists.  The numerical/name codes are:

      # name                description
     -- ----                -----------
      0 plus                +
      1 times               x
      2 box                 box
      3 circ                circle
      4 diamond             diamond
      5 triangleup          triangle with base at bottom
      6 triangleright       triangle with base at left
      7 triangledown        triangle with base at top
      8 triangleleft        triangle with base at right
      9 asterisk            *
     10 star                star of David
     11 filledbox           filled box
     12 bullet              filled circle
     13 filleddiamond       filled diamond
     14 filledtriangleup    filled triangleup
     15 filledtriangleright filled triangleright
     16 filledtriangledown  filled triangledown
     17 filledtriangleleft  filled triangleleft

draw symbol legend
..................

     `draw symbol legend \symbol_name "label" \
         at .x. .y. [cm]'

Draw indicated symbol at indicated location, with the indicated label beside it.  The label is drawn one M-space to the right of the symbol, vertically centered on the indicated .y. location.

draw symbol
...........

     `draw symbol [[.code.|\name]    \
         | [graylevel z]             \
           [color [hue z|.h.]        \
                  [brightness .b.]   \
                  [saturation .s.]]]'

With no optional parameters, draw symbols at the (x,y) data.  If a z-column has been read with read columns, then its value codes the symbol to draw, according to the table below.  (The value of z is first rounded to the nearest integer.)  If no z-column has been read, the symbol X is drawn at each datum.

With the optional numerical/name code specified, then the symbol of that number or name is drawn at each (x,y) datum, whether or not a z-column exists.  The numerical/name codes are:

      # name                description
     -- ----                -----------
      0 plus                +
      1 times               x
      2 box                 box
      3 circ                circle
      4 diamond             diamond
      5 triangleup          triangle with base at bottom
      6 triangleright       triangle with base at left
      7 triangledown        triangle with base at top
      8 triangleleft        triangle with base at right
      9 asterisk            *
     10 star                star of David
     11 filledbox           filled box
     12 bullet              filled circle
     13 filleddiamond       filled diamond
     14 filledtriangleup    filled triangleup
     15 filledtriangleright filled triangleright
     16 filledtriangledown  filled triangledown
     17 filledtriangleleft  filled triangleleft

With the optional graylevel z fields specified, the graylevel is given by the z column (0=black, 1=white).

With the optional color field specified, the color is specified, either directly in the command (the hue .h. form) or in the z column.  For more information on color, refer to the set color hsb ... command.

Examples: both draw symbol bullet color and draw symbol bullet color hue z draw bullets whose hue is given by the value in the z column.  The hue (or the color, in other words) blends smoothly across the spectrum as the numerical value ranges from 0 to 1.  The value 0yields red, 1/3 yields green, 2/3 yields blue, etc. If the brightness and the saturation are not specified, they both default to the value 1, which yields pure, bright colors.

Example: draw all in green dots draw symbol bullet color hue 0.333 brightness 1 saturation 1

Example: display spectrum of dots

     set symbol size 0.3
     open "awk 'END{ \
         for(c=0;c<1;c+=1/40) \
             print(c,c,c)}' | "
     read columns x y z
     close
     draw symbol bullet color hue z

draw time stamp
...............

     `draw time stamp \
         [fontsize .points. \
             [at .x_cm. .y_cm. cm \
                 [with angle .deg.]]]'

Draw the command-file name, PostScript file name, and time, at the top of graph.  Normally, the timestamp is drawn at the top of the page, in a fontsize of 10 points.  But the user can specify the fontsize, and additionally the location (in cm) and additionally the angle measured in degrees anticlockwise from the horizontal.

NOTE: If you want to have the plot drawn in landscape mode, ensure that set page landscape precedes draw time stamp.

draw title
..........

     `draw title "\string"'

Draw the indicated string above the plot.

draw values
...........

     draw values                 \
         [.dx. .dy.]             \
         [\format]               \
         [separation .xcm. .ycm.]

Draw values of z column, at corresponding (x, y) locations.  If the separation keyword is present, the distance between successive points is checked, and points are skipped unless the x and y separations exceed the indicated distances.

  * draw values Draw the values of z(x,y), positioned 1/2 M-space to the right of (x,y) and vertically centred on y.  The values are written in a good general format known as %lg, in C terminology.

  * draw values %.2f Draw values of z(x,y) positioned as described above, but using the indicated format string.  This format string specifies that 2 numbers be used after the decimal place, and that floating point should be used.  See any C manual for format codes.

  * draw values .dx. .dy. Print values of z(x,y) at indicated offset vector (.dx.,.dy.), measured in centimeters, from the values of (x,y) at which the data are defined.

  * draw values .dx. .dy. %.3f Print values of z(x,y) at indicated distance from (x,y), indicated format.

draw x axis
...........

     draw x axis [at bottom|top|{.y. [cm]} [lower|upper]]

Draw an x axis, optionally at a specified location and of a specified style.

  * draw x axis Draw a lower x axis (ie, one with the numbers below the line) at the bottom of the box defined by set y axis.

  * draw x axis at bottom Draw a lower x axis (ie, one with the numbers below the line) at the bottom of the box defined by set y axis.

  * draw x axis at top Draw an upper x axis (ie, one with the numbers above the line) at the top of the box defined by set y axis (or above any existing stacked x axes there)

  * draw x axis at .y. Draw a lower x axis at indicated value of .y..

  * draw x axis at .y. upper Draw an upper x axis at indicated value of .y.

draw x box plot
...............

     draw x box plot at .y. [size .cm.]

Draw Tukey box plots (which give a summary of histogram properties). Box plots were invented by Tukey for eda (exploratory data analysis). The centre of the box is the median.  The box edges show the first quartile (q1) and the third quartile (q3).  The distance from q3 to q1 is called the inter-quartile range.  The whiskers (i.e., the lines with crosses at the end) extend from q1 and q3 to the furthest data points which are still within a distance of 1.5 inter-quartile ranges from q1 and q3.  Beyond the whiskers, all outliers are shown: open circles are used for data within a distance of 3 inter-quartile ranges beyond q1 and q3, and in closed circles beyond that.

As a side effect, this command stores q1, q2, and q3 into variables ..q1.., ..q2.., and ..q3...

  * draw x box plot at .y. Draw Tukey's box plot, spreading in the x direction, centered at y=.y. and of default width 0.5 cm.

  * draw x box plot at .y. size .cm. Draw Tukey's box plot, spreading in the x direction, centered at y=.y. and of width .cm. centimetres.

draw y axis
...........

     draw y axis [at left|right|{.x. cm} [left|right]]

Draw a y axis, optionally at a specified location and of a specified style.

  * draw y axis Draw a left-hand-side y axis (ie, one with the numbers to the left of the line) at left of box defined by `set x axis'

  * draw y axis at left Draw a left-hand-side y axis (ie, one with the numbers to the left of the line) at left of box defined by set x axis.

  * draw y axis at right Draw a right-hand-side y axis (ie, one with the numbers to the right of the line) at right of box defined by set x axis.

  * draw y axis at .x. Draw a left-hand-side y axis (ie, one with the numbers to the left of the line) at indicated value of .x.

  * draw y axis at .x. right Draw a right-hand-side y axis (ie, one with the numbers to the right of the line) at indicated value of .x.

draw y box plot
...............

     draw y box plot at .x. [size .cm]

Draw Tukey box plots (which give summary of histogram properties).

  * draw y box plot at .x. Draw Tukey's box plot, spreading in the y direction, centered at x=.x. and of default width 0.5 cm.

  * draw y box plot at .x. size .cm. Draw Tukey's box plot, spreading in the y direction, centered at x=.x. and of width .cm. centimetres.

As a side effect, this command stores q1, q2, and q3 into variables ..q1.., ..q2.., and ..q3...

draw zero line
..............

     draw zero line [horizontally|vertically]

Draw lines corresponding to x=0 or y=0.

  * draw zero line Draw line y=0 if it is within axes.

  * draw zero line horizontally Draw line y=0 if it is within axes.

  * draw zero line vertically Draw line x=0 if it is within axes.

end grouip
..........

     end group

Command not implemented yet.  Syntax may change.

expecting
---------

     expecting version a.b
     expecting version a.b.c

Show a list of incompatibilites that have been introduced since the named version.  This command can make your commandfiles more reliable against changes to Gri.

There are two forms of the version number.  Modern versions use the triplet form, e.g.  expecting version 2.8.7, but prior to October 1996 the version numbers were written in decimal form, so that you would write expecting version 1.069 for example.

filter
------

  * filter column x|y|z|u|v|weight recursively a[0] a[1] ... b[0] b[1] ... Filter indicated column, using a two-pass recursive filter.  The first pass runs from the start to the end, while the second pass runs from the end to the start; in this way, the phase shift inherent in this type of filter is removed entirely.  The coefficients are used in the following formula (demonstrated on the x column):

          x_new[i] = b[0] * x[i] \
            + b[1] * x[i-1] \
            + b[2] * x[i-2] \
            + ... \
            - a[1] * x_new[i-1] \
            - a[2] * x_new[i-2] \
            - ...

     Thus, for example, setting a[i] = 0 results in a simple backwards-looking moving-average filter applied in two passes.  The real power of this type of filter, however, comes when non-zero a[i] coefficients are given, thus adding recursion (i.e., x_new[i] depends on x_new[i-...]).  See any standard reference on digital filters for an explanation.  You might find that the Matlab command butter an easy way to design filter coefficients.  Here are some examples:

          # Filter x column with simple 2-point moving
          # average.  (This slurs into a 3-point moving
          # average, in effect, since the filter is run
          # forwards and then backwards.)
          filter column x recursively 0 0 0.5 0.5

          # Use filter designed with the Matlab
          # command butter(2,0.1), which creates a
          # 2nd order lowpass butterworth filter
          # with a cutoff frequency of 0.1
          # (in units which have a frequency
          # of 1 corresponding to one-half the
          # sampling rate).
          filter column x recursively \
              1     -1.561  0.6414 \
              0.0201 0.0402 0.0201

  * filter grid rows|columns recursively a[0] a[1] ... b[0] b[1] ...

     Apply recursive filter (see filter column ... recursively for meaning of this filter operation) to the individual rows or columns of the grid data.  For example, the command filter grid columns recursively 0 0 0.5 0.5 applies a 2-point moving average filter across the columns, smoothing the grid in the x-direction.

  * filter image highpass Remove low-wavenumber components from image (ie, sharpen edges).  Do this by subtracting a Laplacian smoothed version of the image.

  * filter image lowpass Remove high-wavenumber components from image (ie, smooth shapes).  Do this by Laplacian smoothing.

See also Smooth.

flip
----

     `flip grid|image x|y'

Flip grid or image by relecting it about a horizontal or vertical centerline.

  * flip grid x Flip grid so right-hand side becomes left-hand side.

  * flip grid y Flip grid so bottom side becomes top side.

  * flip image x Flip image so right-hand side becomes left-hand side.

  * flip image y Flip image so bottom side becomes top side.

get env
-------

     `get env \result \environment_variable'

Get the value of an "environment variable" from the unix operating system, and store the result in the indicated synonym.  This makes most sense on unix systems (hence the name, patterned after the unix command getenv).  This command can be useful in making gri programs resistant to changes in data-file locations.  Suppose, for example, there is a file called data, normally in a local directory called Bravo.  The line open Bravo/data will fail if the Bravo directory is moved.  But if the name of the datafile is stored in an unix environment variable, DIR_BRAVO say, then the gri program will work no matter where the Bravo data are moved, so long as an appropriate environment variable is modified when the data are moved.  Example:

     get env \dir DIR_BRAVO
     if {rpn "\dir" "" ==}
         show "Cannot determine location of the Bravo data,"
         show "which should be stored in the environment"
         show "variable DIR_BRAVO.  You should"
         show "do something like"
         show "export DIR_BRAVO='/data/Bravo/'"
         show "in your ~/.environment file"
         quit
     end if
     open \dir/data
     ...

group
-----

     `group ["\name"]'

Command not implemented yet.  Syntax may change.

heal
----

     heal columns|{columns along x|y}

The heal command heals over gaps in either columnar or gridded data.  This is done by linear interpolation across the missing-value gaps.

  * heal columns

     Fill in missing values in x, y, z, ... columns, by linear interpolation to neighboring valid data.  All gaps in the data will get replaced by a linear function of index which matches the data at the indices just before and just after the gap.  For example, if the y data were like

          111
          3
          -9
          -9
          -9
          7
          333

     where -9 is the missing-value code, then they would get replace by

          111
          3
          4
          5
          6
          7
          333

     Notes: (1) This is done independently for all existing columns. (2) Gaps at the start and end of the columns are not filled in.

  * heal grid along x

     Scan in the x direction, filling in missing values by linear interpolation.  Since this uses the the x-grid, you must first have done read grid x or set x grid.

  * heal grid along y

     Scan in the y direction, filling in missing values by linear interpolation.  Since this uses the the y-grid, you must first have done read grid y or set y grid.

help
----

     `help [*|command_name|{- topic}]'

Give help on a command or topic.

  * help Print a general help message.

  * help * Prints complete help info.

  * help command_name Prints help on the command whose name begins with the string command_name.  The string may be several words long; e.g. help set or help set x axis.

  * help - topic_name The minus sign tells Gri that the string to follow it is a topic, not a command.  Topics Gri knows about are listed by the one-word help request.

if
--

(See also If Statements.)

     `if {[!] .flag.}|\flag|{{"string1" == "string2"}}'

Control program flow.  The if block is ended with a line containing end if.  Optional else and else if blocks are allowed.  Note that rpn expressions are allowed, and a special form of string comparison is allowed, as in the examples below.

     if .flag.
       # List of Gri commands to be done if .flag. is 1.
       # This list may extend across any number of lines.
     end if

If the variable .flag. is not equal to 0, do the code between the if line and the end if line.

     if .flag.
       # Commands done if .flag. is 1
     else
       # Commands done if .flag. is 0
     end if

If the variable .flag. is not equal to 0, do the code between the if line and the else line.  If .flag. is equal to 0, do the code between the else line and the end if line.

     if ! .flag.
       # Commands done if .flag. is 0
     end if

If the variable .flag. is equal to 0, do the code between the if line and the end if line.

     if {rpn .flag. 10 <}
       # Commands done if 10 is less than .flag.
     end if

If the variable .flag. is greater than 10, do the code between the if line and the end if line.

     if \smooth
       # Commands done if \smooth is 1
     else
       # Commands done if \smooth is 0
     end if

If the number stored in the synonym \smooth is not equal to 0, do the code between the if line and the else line.  If the synonym stores a representation of a number not equal to zero, do the else part.  If the synonym contains text that does not decode to a number, generate error message.

     if {"\item" == "Temperature"}
       # Commands done if the synonym \item is equal to the
       # indicated text string.
     end if

If the synonym \item has the value Temperature stored in it, do the indicated code.

     if {rpn "\item" "Temperature" ==}
       # Commands done if the synonym \item
       # equals indicated text string.
     end if

As above, but using the rpn calculator (rpn Mathematics).

     if {rpn "\item" "Temperature" !=}
       # ...
     end if

As above, but do the indicated code if \item is not equal to Temperature.

ignore
------

     `ignore last .n.'

Ignores last .n. lines read by read columns.

input
-----

     `input \ps_filename \
       [.xcm. .ycm. \
         [.xmag. .ymag. \
           [.rot_deg.]]]'

Input the named PostScript file directly into the Gri output PostScript file.  (If the filename has punctuation, insert it in double quotes, e.g. input "../thefile".)  If no options are specified, the file is input at normal scale, with normal margins.  (Aside to PostScript programmers: the named file is sandwiched between gsave and grestore commands.)  If .xcm. and .ycm. are specified, then the origin is moved to the named location first.  If, in addition, .xmag. and .ymag. are specified, then these are used as scale factors after translation.  Finally, if .rot_deg. is specified in addition, then the indicated counterclockwise rotation is applied after translation and scaling.  Hint: if the results look wrong, the first thing to do is to think carefully about the order of the (translation, scaling, rotation) operations.

insert
------

     `insert \filename'

Perform the commands in the indicated file.

If the file name is absolute (i.e. starts with ., or with / or with ~) then an error results if the file is not present (or cannot be read by this user).

However, if the file name starts with a normal letter, Gri will try harder to locate the file.  If it is not in the local directory, and if a set path to "PATH" for commands has been done, then Gri will search the colon-separated directories for the file (Set Path To).

If you don't want path-searching done, use the source command instead (Source).

interpolate
-----------

     interpolate x grid to .left. .right. .inc.|{/.cols.}'
     interpolate y grid to .bottom. .top. .inc.|{/.rows.}'

Transform grid by interpolating between existing grid data, according to a new x or y grid specified in the manner of set x grid and set y grid.  Note that the new grid is neccessarily regular, while the first grid needn't have been.  The data of the new grid are constructed by interpolation, using the same interpolation algorithm as the convert grid to image command.

list
----

     `list \command-syntax'

List the source of a gri command.  Often this is just the name of a C function internal to gri (try list list for an example), but when the command is written in the gri programming language the source will be more understandable (try list set panel).

ls
--

     `ls [\file_specification]'

List files in current directory.  (The current directory can be printed by the gri command pwd and can be set by the gri command cd.)  ls \file_specification lists files in current directory which match the file specification.  Normal unix file specification options are understood.

mask
----

     `mask the image [to {uservalue .u.}|{imagevalue .i.}]'

Examine both the image and the mask pixel by pixel.  For any pixels which have a mask value of 1 (which indicates an invalid region of the image), change the image value.  If no to phrase is present, change the image value to 0 in pixel units.  If the to uservalue .u. phrase is present, change the pixel to hold the imagevalue that corresponds to this uservalue (see set image range command for a discussion of this correspondance).  If the to imagevalue .i. phrase is present, change the pixel to hold that imagevalue (in range 0 to 255 inclusive for 8-bit images).

new
---

     new .variable_name. | \synonym_name \
        [.variable_name. | \synonym_name \
        [...]]

new sets aside storage for new version of the named variable(s) and/or synonym(s).  Any number of variables and synonyms may be specified.  If a given variable/synonym already exists, this will create a new version of it, and future assignments will be stored in this new version without affecting the pre-existing version.  If the variable/synonym is deleteed, the new version is deleted, making the old, unaltered, version accessible again.

This command is used mostly for temporary use, to prevent clashing with existing values.  Suppose you want to change the font size inside a new command or an if block.  Then you might do the following, where the variable .tmp. is used to store the old font size.  Note that the use of the new/delete statements prevents the assignment to the local version of the variable .tmp. from affecting the value known outside the if block, if in fact .tmp. happened to exist outside the block.

     set font size 10
     draw label "This is in fontsize 10" at 10 2 cm
     if .want_title.
       new .tmp.
       .tmp. = ..fontsize..
       set font size 22
       draw label "This is 22 font" at 10 5 cm
       set font size .tmp.
       delete .tmp.
     end if
     draw label "This is 10 font" at 10 8 cm

Special case: for local synonyms (e.g. \.word1., etc.), the new operator checks to see whether the synonym is standing for an "ampersand" argument, signalling a changeable argument that is a variable or a synonym.  In such a case, new creates a new instance of the item in the calling context.  The test suite has examples (Test Suite).

new page
--------

     `new page'

Finish the present page, and start a new page.  All settings (of linewidth, axes, landscape/portrait, etc) are retained on the new page. Among these settings is the flag that tells gri whether you need axes plotted along with your data.

new postscript file
-------------------

     `new postscript file "name"'

Finish the present Postscript file, and start a new page with the given name.  All settings (of linewidth, axes, landscape/portrait, etc.) and data are retained on the new file.

open
----

There are two styles of open command.  In the first style, a simple file is to be opened.  In the second style a unix-like "pipe" is opened, i.e. Gri will read the output of a system command instead of a file.

Opening simple files
....................

Ascii Files Most applications involve ascii files, and these are very easy to handle in Gri.  For example given a data file named foo.dat, just use the command

     open foo.dat

and then you can read the data using various commands.  Thus a complete program might be

     open foo.dat
     read columns x y
     draw curve

If a filename contains blanks or punctuation symbols, you must put it in double quotes ("), e.g.

     open "foo bar.dat"

Indeed, Gri accepts double-quotes on any open command and some folks use it on all commands, as a matter of habit.

Gri can handle compressed files appropriately, e.g.

     open foo.data.gz

so that there is no need to uncompress data for use with Gri.

Gri is quite persistant in looking for your file, and if a given file is not found, it will then check to see if a compressed version is available, and use that instead.  Thus

     open foo.dat

will look for a file named foo.dat.gz if foo.dat is not available.  (Only files compressed with the GNU gzip utility are handled.)

If the open command was successful in opening the file, it will set the value of the synonym \.return_value. to the full pathname of the file.  Thus, if open a.dat is done in directory /home/gri, then \.return_value. will equal the string /home/gri/a.dat.

Binary Files Like most computer programs, Gri has some trouble with binary files. One big issue is the so-called "endian" character of the computer.  Some computers store multi-byte values with the most significant bytes first, while others store them with the most significant bytes last.  The problem is that nothing is stored in data files to indicate which convention was employed.  For this reason, a version of Gri compiled on a so-called "big-endian" computer will misinterpret multi-byte values that were created on a so-called "little-endian" computer.  Many folks in the scientific community have converted to using the NetCDF format (see next section) for precisely this reason, since this format is independent of the endian character of the computer.

Presuming an appropriate endian character, however, reading is straightforward.  A command of the form

     open foo.dat binary

tells Gri that the data are stored in a binary format.  With the above syntax, Gri expects images to be in unsigned char (8 bits), while other data, such as columns and grids, are expected to be in 32-bit format (suitable for reading into a so-called "float" variable in the C programming language).

You may also specify the format directly, as in the following examples; Gri then interprets all data as being in the indicated format and then converts to the internal format before using the data.

     open \filename binary uchar
     open \filename binary 8bit
     open \filename binary int
     open \filename binary float
     open \filename binary double
     open \filename binary 16bit

As with ascii files, Gri will automatically uncompress any files that are compressed, and if it fails to find a given filename, it will try to open a compressed version of it (i.e. one with a .gz suffix).

NetCDF Files The NetCDF format provides the best of both worlds.  It is binary, so that data are relatively compact, and may be read very quickly. (Reading ascii data is time-consuming in C++, the language in which Gri is written.)  But it does not suffer the endian problem problem of normal binary files (see previous section), since information about the endian character is stored in the file itself, and Gri uses this information to decode the data without difficulty, regardless of the endian characteristics of the computer on which Gri is running and of the computer that created the data.

For more information on netCDF format, see

http://www.unidata.ucar.edu/packages/netcdf/index.html

The syntax of opening NetCDF files is as below

     open foo.nc netCDF

and the syntax for reading such files is described in sections on the various read commands (see e.g. Read Columns).

Opening pipes
.............

Sometimes it makes sense to get Gri to work with the results of another command in the OS.  Gri handles this by creating a so-called "pipe", thus reading the output from the other command.  (Readers familiar with the unix OS will know what pipes are all about, and especially why they are a good thing.  Other readers might wish to skip this section.)

Suppose we wish to plot an x-y plot using just the first few lines of a datafile named foo.dat.  Unix users will know that a good way to see the first few lines of such a file would be to type the command head foo.dat.  They also know that these lines could be provided to a second unix command, named do_foo say, by the command head foo.dat | do_foo.  This uses a so-called "pipe", designated by the vertical line (called a pipe symbol below).

Gri can read the output from system commands by using a syntax in which the (quoted) system command ends in a pipe symbol, e.g.

     open "head foo.dat |"

as in the example above.

Aside: When pipe-open commands are used, Gri creates a temporary file (often located in /usr/tmp, but that varies with machine). This is automatically cleaned up when Gri completes executation, but if Gri dies (or is interrupted) before it finishes, you'll be left with an extra file in this temporary-storage directory.  It's up to you to clean that directory up from time to time.

Some common examples of pipe-open commands are given below.

 1. Comma-separated values are common in files created by, or intended for, spreadsheets.  Since Gri expects data elements to be separated by blanks (or tabs), you'll have to convert the commas into blanks.  There are many ways to do that using pipes, e.g. sed system utility, e.g.

          open "sed -e 's/,/ /g' foo.dat |"

     Other unix facilities, such as tr will also work, of course.  If the file has headers, you'll want to remove them also.  This can be done with the skip command (Skip) but you could also do it at the open stage, e.g. to remove the first two lines, use

          open "sed -e 's/,/ /g' foo.dat | tail +2 |"

 2. Manipulating column data is done by e.g.

          open "cat foo.dat | awk '{$1, $2 * 22}' |"

     where awk has been used to multiply the second column in the file named foo.dat by 22.

 3. Time-based and geographical data are sometimes encountered.  For an example, suppose that longitude/latitude (i.e. x/y) data are stored in Hour.minutesecond format, e.g. 12.2133 means hour 12, minute 21, second 33.  Gri doesn't read HMS format, but gawk can be told to:

          open "cat datafile.HMS |        \
              awk '{                      \
              split($1, hms, \".\");      \
              h = hms[1];                 \
              m = int(hms[2] / 100);      \
              s = hms[2] - 100 * m;       \
              x = h + m / 60 + s / 3600;  \
              split($2, hms, \".\");      \
              h = hms[1];                 \
              m = int(hms[2] / 100);      \
              s = hms[2] - 100 * m;       \
              y = h + m / 60 + s / 3600;  \
              print(x,y)                  \
              }' | "
              read columns x y

 4. Timeseries data are often stored in formats that blend letters and numbers.  For one thing, using letters (e.g. aug) removes an ambiguity in numerically-based data.  (Example: 02/03/2000 means one thing to an American and another thing in the rest of the world. However, everybody agrees on what 2000-Feb-03 means.)  Suppose, for example, that we have data in a format such as

          Tue_Jul_25_11:07:51 0.62
          Tue_Jul_25_11:22:51 0.59
          Tue_Jul_25_11:37:51 0.56

     (stored in a file called foo.dat say) and we want a graph of the y-variable (0.62, 0.59, 0.56) versus x-variable, time expressed say as seconds in the day.  Then here is how that could be done:

          open "cat foo.dat |\
              sed -e 's/_/ /g' -e 's/:/ /g' |\
              awk '{print ($4*3600+$5*60+$6, $7)}' |"
          read columns x y
          draw curve

     Note that the actual day information is skipped in this example; seasoned awk users could easily fill in the code to handle datasets spanning several days.

Opening URLs
............

Gri can open a URL, if you have the wget program on your machine.  (wget is available from the GNU website http://www.gnu.org/software/wget/.)

The URL must be enclosed in quotes (since otherwise, Gri will interpret the // sequence as indicating an old way of denoting comments).  For example,

     open "http://gri.sourceforge.net/gridoc/examples/example1.dat"
     read columns x y
     show columns

If you don't have wget installed on your machine, the above won't work, but you can always use another fetching program, with a system call, as in the following:

     \url = "http://gri.sourceforge.net/gridoc/html/examples/example1.dat"
     open "lynx -dump \url |"
     read columns x y
     draw curve

postscript
----------

     `postscript \string'

Write the indicated string to the PostScript output file, after substitution of synonyms if there are any.  Example:

     \a = "45"  # angle
     \w = "8.5" # page width
     postscript gsave \w 72 mul 0 translate \a rotate
     # ... other code to do stuff
     postscript grestore

Here is how to draw an image palette vertically instead of horizontally:

     \X = "3"	# cm
     \Y = "10"	# cm
     \a = "90"       # degrees counterclockwise
     postscript gsave \X 28.35 mul \Y 28.35 mul translate \a rotate
     # Palette is at user's origin
     draw image palette box 0 0 10 1
     postscript grestore

NOTE: the postscript command is very dangerous, and should normally only be used by developers.  Most of the code concerning this is in the file doline.cc; look for the string postscriptCmd to find the relevant code.

pwd
---

     `pwd'

Print current directory (which can be set by cd).

query
-----

     `query \synonym|.variable. \
       ["\prompt" ["\default"|.default.]]'

Ask the user for the value of a variable (number) or synonym (text string).  Gri recognizes the type of the item being asked for, either a variable or synonym, by the presence of a dot or backslash in the second word of the command line.  If a prompt string is given (in quotes), then this string is shown to the user.  If a default is given (in parentheses), then it will be displayed also, and if the user types carriage-return, then that item will be assigned to the variable or synonym.  If the default has more than one item, then Gri considers this a restrictive list of possibilities, and will demand that the answer be in that list, going into an infinite query loop until an item from the list (or carriage-return, meaning take first item) is found.  The items in the list are to be separated by spaces, not commas or any other non-whitespace characters.

NOTE: The -y command-line option bypasses all query commands, fooling Gri into thinking that the user typed a carriage-return to all questions.  Thus the defaults, if they exist, are selected.

quit
----

     `quit [.exit_status.]'

Exits the gri program.  If an exit status (.exit_status.) is specified, then Gri returns this value, rounded to the nearest integer, as the ``exit status'' (a concept meaningful mostly in the unix environment, where it designates an error).

The read commands
-----------------

There are several varieties of read command.  Those commands used for reading numerical information (e.g. read columns) are able to decode variables and synonyms as well as simple numbers.

read colornames
...............

     `read colornames from RGB ["\filename"]'

With no filename given, reads an X11-format rgb.txt file that is provided with gri.  Otherwise, reads the named file and tries to interpret it as an X11 file.  The file format has 4 or more columns, the first three giving the red, green and blue values in the range 0 to 255, and the last columns giving the colorname (which may have more than one word). Once you have read in a colorname table, the named colors may be used as builtin colors (Set Color).  To view the names and RGB values of the colors Gri knows, including builtin ones and ones from read colornames, use show colornames.

This command is akin to set colorname (Set Colorname), except that the latter uses the Gri notation of color constituents being in the range from 0 to 1, whereas for read colornames uses an X11 database, so that the color constitutents range from 0 to 255.

read columns
............

     `read columns ...'

Read numbers into columns.  These columns have predefined meanings and names.  For example, read columns x y instructs Gri to read data into columns called x and y; it is these data that Gri will use if you tell it to draw curve.  Other columns are: z, used for contouring a function z=z(x,y); weight, used for weighting data points; u and v, used for arrow (vector) plots.

If the keyword appending is given as the last word on the read columns line, then the new data will be appended to any existing columnar data; otherwise they will overwrite any existing data.

As a special case, if the x column is not indicated (e.g. read columns y) then Gri creates x-values automatically, in the sequence 0, 1, 2, etc.

  * read columns x y Read x in column 1, y in column 2 until blank-line found. Only the first two numbers on each line will be read; any extra numbers (or words) on the line will be ignored.

  * read columns * y * * x Read x in column 5, y in column 2.  The * character is a spacer.  It instructs Gri to skip the first, third, and fourth words on the data line.  These words need not be numbers.  This example illustrates a general mechanism of using the * character to skip over unwanted items in the data file.  Note that there is no need to supply * characters for trailing extraneous words; Gri will skip them anywary.  Finally, note that any order of x and y (and the other columns; see below) is allowed.

  * read columns y=2 x=5 or read columns x=5 y=2 As above; read x in column 5 and y in column 2.  The column number may be specified in this manner for all the named column variables.  No spaces are allowed before or after the = sign. The first column is called column 1.  Whether this format is used or the * format is a matter of choice, except that numbered format also permits using a given number to fill several variables (for example read columns x=1 y=2 u=1 v=2).

  * read columns x="netCDF_name" ... If the file is a netCDF file, opened by e.g. open myfile.nc netCDF, then the netCDF variables for the columns, e.g.

          open latlon.nc netCDF
          read columns x="longitude" y="latitude"

     Note: the data must be stored as the netCDF ``float'' type.

     For more information on netCDF format, see

     http://www.unidata.ucar.edu/packages/netcdf/index.html

  * read columns * y z * x Read x in column 5, y in column 2, and z in column 3.  The z column is used for contouring.

  * read columns x y u v Read x and y in first two columns, and the ``arrow'' data u and v as third and fourth columns.

  * read columns .rows. x y Read .rows. rows of column data.

Sometimes you'll have x in one file and y in another.  In that case, use the operating system or an editor to put the columns in one file.  In unix, the easy way is

     open "paste file_with_x file_with_y |"
     read columns x y

NOTE FOR BINARY FILES: For ascii files, Gri will proceed to a new line after it has read the items requested; it skips any words appearing on the data line after the last object of interest.  Thus read columns x y will read the first two columns and ignore any other columns that might be present.  But for binary files, Gri has no way of knowing how to "skip" to the next line (see skip command), so you will have to flesh out the read columns command with as many spacers as are present in your data.  For example, if you have four numbers in each data record and want to interpret the first two as x and y, you would use read columns x y * * to read the data.

RETURN VALUE: Sets \.return_value to N rows N non-missing N inside-clip-region

read grid
.........

read grid commands read grid characteristics.  (The ``grid'' is the object that is contoured.)

For normal ascii or binary files, the commands to read the grid's x-locations, y-locations and data are:

     `read grid x [.rows.]'
     `read grid y [.rows.]'
     `read grid data [spacers] \
       [.rows. .cols.] [spacers] [bycolumns]'

For netCDF files, the commands are as follows (note that it is not possible to specify the number of data to read, nor to read the grid by columns).

     `read grid x = "variable_name"'
     `read grid y = "variable_name"'
     `read grid data = "variable_name"'

The ordering of the y-grid data is the same as if they were read from a normal file: the first number is considered to be at the top of the plot.

For more information on netCDF format, see

http://www.unidata.ucar.edu/packages/netcdf/index.html

Details of the non-netCDF commands:

  * read grid x [.cols.] Read the x locations of the grid points, one number per line. If .cols. is supplied, then that many values will be read; otherwise, reading will stop at end-of-file or blank-line.

  * read grid y [.rows.] As above, but for y grid;  .rows. is the number of rows.  The first number to be read corresponds to the location of the top edge of the grid.  Thus, if you were to view the column of numbers with a text editor, they would be oriented the same way as the corresponding elements will appear on the page.

  * read grid data [.rows. .cols.] Read data for a grid having .rows. and .cols. columns. (If .rows. and .cols. are not supplied, but the grid already exists, then those pre-existing values are used.  If they are specified here, then they are checked for consistency with the pre-existing values if they exist.) Gri will read .rows. lines, each containing .cols. numbers.  (Extra information in the file can be skipped; see discussion of the * keyword below.)  Gri will interpret the first line it reads as the grid data corresponding to a value of y equal to y[.rows.].  Thus, file should be arranged like this:

          f(x[1], y[.rows.])  ...  f(x[.cols.], y[.rows.])
                  .
                  .
                  .
          f(x[1], y[3])       ...  f(x[.cols], y[3])
          f(x[1], y[2])       ...  f(x[.cols], y[2])
          f(x[1], y[1])       ...  f(x[.cols], y[1])

  * read grid data [.rows. .cols.] bycolumns As above, but the bycolumns keyword tells Gri to read the data one column at a time, instead of one row at a time.  Each line is expected to contain .rows. numbers (as opposed to .cols. numbers, as in the format where the bycolumns keyword is not present).  (Extra information in the file can be skipped; see discussion of the * keyword below).  The first line of the data file contains the first column of the gridded data, corresponding to x equal to x[1]).  The file should look like this:

          f(x[1], y[1])     ...     f(x[1], y[.cols.])
          f(x[2], y[1])     ...     f(x[2], y[.cols.])
          f(x[3], y[1])     ...     f(x[3], y[.cols.])
                  .
                  .
                  .
          f(x[.rows.],y[1]) ...  f(x[.rows.], y[.cols.])

  * read grid data * * [.rows. .cols.] As read grid data .rows. .cols. except that the first two words on each line are skipped.  As usual, trailing extraneous numbers are also skipped.

See also set x grid, set y grid

RETURN VALUE:

read grid x sets \.return_value to N cols

read grid y sets \.return_value to N rows

read grid data sets \.return_value to N rows N cols

read image colorscale
.....................

     `read image colorscale [rgb|hsb]'

Read colorscale for image, from 256 lines each containing values for Red, Green, and Blue (or Hue, Saturation and Brightness), separated by whitespace.  The values are expected to be in the range 0 to 1, and are clipped to these limits if not.

For hints on how to create such an input file, Read Image Grayscale.  If the example given there has the following code instead,

     open "awk 'BEGIN {               \
          for(i=0;i<256;i++) {        \
            print((i - 50)/50, 1, 1)  \
          }                           \
        }' |"
     read image colorscale hsb

then a linear full-color spectrum running from red at 10C to magenta at 15C is achieved.

read image grayscale
....................

     `read image grayscale'

Read grayscale for an image, from 256 lines each containing a single value.  The values are expected to be in the range 0 to 1, and are clipped to these limits if not.  For 8-bit images, Gri multiplies these values by 255, and uses this list for the grayscale mapping.  Such a list is created by write image grayscale.

As an example, consider the code fragment (Images).

     set image range 5 30.5
     set image grayscale black 10 white 15

is equivalent to

     set image range 5 30.5
     open "awk 'BEGIN {\
       for(i=0;i<256;i++) {\
         print(1-(i-50)/50)\
       } \
     }' |"
     read image grayscale
     close

because the image formula is

     Temperature = 5C + 0.1C * pixelvalue

where the pixelvalue ranges from 0 to 255.  Therefore, a temperature of 10C is a pixelvalue of 50, and 15C is 100.  To get a grayscale ranging between these values, therefore, we create a linear function which maps the 50th pixelvalue into grayvalue 1, and the 100th pixelvalue into grayvalue 0.  That is what the awk line does; to see the actual numbers, you could insert the line write image grayscale to TMP and look at the file TMP (bear in mind that Gri will clip the values to the range 0 to 1).

Sometimes you will have a file, say named map.dat, with RGB numbers in the range 0-255, rather than 0-1 as Gri requires.  To read them, use the operating system to convert the numbers for you (Open).

     open "cat map.dat \
       | awk '{print(($1+$2+$3)/3/255)}' |"
     read image grayscale
     close

read image mask
...............

     `read image mask rasterfile|{.rows. .cols.}'

Read image mask.  The mask is associated with the image read in by the read image command in the following way.  When computing image histograms, Gri ignores any pixels in the image for which the corresponding pixel in the mask is set to 1.

  * read image mask rasterfile The image size is specified in the rasterfile file itself, so it is not specified.

  * read image mask .rows. .cols. The file must contain .rows.*.cols. binary data.  Pixel order is the same as for images.

read image
..........

There are several types of read image commands, depending on the file format.  If the file is "raw", with no embedded information about things like the width and height, then we need to specify everything, as in the first format given below.  The other formats make use of the header information in, e.g. PGM files.

Headerless images

     `read image .rows. .cols. \
       [box .xleft. .ybottom. .xright. .ytop.] \
       [bycolumns]'

With no options specified (read image .rows. .cols.), read binary data defining an image.  The image range must have previously have been set by set image range.  The data are as written by "unsigned char" format in C.

When the box option is specified, the geometry of the image, in user coordinates, is specified in terms of the cartesian coordinates of the lower-left corner (.xleft., .ybottom.) and upper-right corner (.xright., .ytop.).  If the box option is not specified, this geometry can be specified with either read x grid or set x grid, plus either read y grid or set y grid.

With the bycolumns keyword present, the image is read sweeping from top-to-bottom, then left-to-right, instead of the usual order.

Sun rasterfile images

     `read image rasterfile [box .xleft. .ybottom. .xright. .ytop.]'

Read image in Sun rasterfile format.  Image geometry is inferred from the header, so .rows. and .cols parameters are not given.

PGM images

     `read image pgm [box .xleft. .ybottom. .xright. .ytop.]'

Read image in PGM (Portable Gray Map) format.  Image geometry is inferred from the header, so .rows. and .cols parameters are not given.  Both ascii and binary PGM formats are supported (that is, files with magic characters of P2 and P5).

NOTE that there are many image formats and Gri doesn't try to deal with them all.  The idea is to use another program to convert images to a file format that Gri understands.  In the future Gri may support PNG and other popular formats, especially in the Linux versions, for which libraries exist to ease the input.

read from \filename
...................

     `read from \filename'

Cause future read commands to read from the indicated file.  If that file is not open, an error message will result.  Use read from \filename to shuffle reading among several open files.

Gri can look up filenames for read from in terms of their full pathnames or their local pathnames.  Thus, a local file called a.dat in the directory /home/gri can be referred to by read from a.dat or by read from /home/gri/a.dat, which comes in handy if you need to work with two files of the same name, in other directories.  However, since Gri has the ability to search for files in a "path" (Set Path To), you may not have specified an exact path name; this is why the open command provides a return value which names the full pathname (Opening Simple Files).

read synonym/variable
.....................

     `read [* [*...]] \synonym|.variable. [\synonym|.variable. [...]]}'

Read one or more items from the next line of the input file.  These items may be synonyms or variables.  The token * indicates that the word in the datafile should be skipped.  As usual, the datafile may be embedded in the commandfile, providing the last data line is blank.

Normally one would use synonyms for words, and variables for numbers. The items are separated by one or more "whitespace" characters (e.g. space or TAB).  Thus, if a file contained the line

     Temperature 10.3

then the line

     read \var_name .var_value.

would have the same result as

     \var_name = "Temperature"
     .var_value. = 10.3

This command ignores any trailing items on the line.  That is, the next read command will start on the next line of the file.  In a sense then, you get just one shot at analysing the input line in your datafile.  If you need flexibility, you may wish to read the whole contents of the line into a synonym, which may be done using the read line command instead, to read it in as a string. (Read Line).

If the input file is in the netCDF format, the indicated item will be read.  For example, read \time:_MissingValue reads the missing value for the variable called time.  This conveniently allows your data file to dictate axes names, units, missing values, etc.  Example:

     # Plot profile of TU81N (age-corrected tritium)
     open profile.nc netCDF
     read columns x="TU81N" y="z"
     read \{z:_FillValue}		# assume same for all
     read \{z:long_name}
     read \{z:units}
     read \{TU81N:long_name}
     read \{TU81N:units}
     close
     set missing value \{z:_FillValue}
     set x name "\{TU81N:long_name} (\{TU81N:units)}"
     set y name "\{z:long_name} (\{z:units)}"
     set y axis decreasing
     draw curve

For more information on netCDF format, see http://www.unidata.ucar.edu/packages/netcdf/index.html

read line
.........

     `read line \synonym'

Read the next line of the datafile (or commandfile), trim off a trailing comment if there is one, and then store the next line of datafile into the named synonym.

regress
-------

     `regress {y vs x [linear]}|{x vs y [linear]}'

Perform linear regression of y as a function of x or x as a function of y.

  * regress y vs x Linear regression of y vs x.  Several quantities are reported and also saved into builtin variables.  The intercept is defined as ..coeff0.., its 95 percent confidence limit is defined as ..coeff0_sig...  Thus the confidence range is ..coeff0..-..coeff0_sig.. to ..coeff0..+..coeff0_sig... Similarly the slope and confidence limit are stored in ..coeff1.. and ..coeff1_sig..

     The squared correlation coefficient is stored in ..R2...

     Historical note prior to version 2.1.15, a different meaning was attached to ..coeff0_sig.. and ..coeff1_sig..; they used be defined as standard errors, without having been multiplied by the appropriate student-t coefficient.

  * regress x vs y Linear regression of x vs y; for notation see above.

  * regress y vs x linear Linear regression of y vs x; for notation see above.

  * regress x vs y linear Linear regression of x vs y; for notation see above.

reorder
-------

     `reorder columns randomly \
       |{ascending in x|y|z} \
       |{descending in x|y|z}'

Reorder the columns in various ways.

In the randomly style, the column data are shuffled randomly by index, retaining the correspondance between a given x and y.  This is useful with draw symbol using colored dots -- it prevents the overpainting of one dot on another from biasing the color field to values that happened to occur near the end of the column data.  If you prefer the overpainting to be done in random order, use this command to reorder the columns randomly.  The random number is selected using the system rand call, with the seed being provided by the PID (process ID) of the job.

The ascending and descending styles do what you'd expect.

rescale
-------

     `rescale'

Re-determine the scales for the x and y axes.  Typically used after a column math operation, when you want the new data to be auto-scaled. (Note: normally, if the axes have already been drawn, Gri won't rescale automatically just because you modify the column data.  This is designed so that you can add offsets to curves, etc, while staying in saved axes. But if the axes have not been drawn yet when you modify the column data, then Gri will automatically rescale the axes it is planning to draw.)

resize
------

     `resize {x for maps}|{y for maps}'

Resize the axes frame region in such a way that geographical objects appear in correct proportions.  This assumes that y is degrees latitude and x is degrees longitude.

  * resize x for maps Resize the plot width for maps, assuming that x represents longitude and y represents latitude.  Before using this, you must have defined scales for both x and y, and a size for y (ie, you must have done set x axis ..., set y axis ... and set y size); this command sets the x size, thus eliminating set x size. The result is that, at the central latitude (y), a centimetre on the page will correspond to an equal distance on the earth, in both the north-south and east-west directions.

  * resize y for maps Resize the plot height for maps, assuming that x represents longitude and y represents latitude.  Before using this, you must have defined scales for both x and y, and a size for x (ie, you must have done set x axis ..., set y axis ... and set x size); this command sets the y size, thus eliminating set y size. The result is that, at the central latitude (y), a centimetre on the page will correspond to an equal distance on the earth, in both the north-south and east-west directions.

     See also resize x for maps.

return
------

     `return'

Return early from a user-defined function or an insert file.  Or, in the main gri program, do the same thing as quit.

rewind
------

     `rewind \filename'

Rewind a data-file to the beginning.  If no filename is given, this is done for the currently active file; otherwise the named file is rewound.

rpnfunction
-----------

     `rpnfunction name replacement-words'

Create a new keyword for use in rpn expressions.  Inside any RPN expression which follows this line, the word name will be substituted with the indicated replacement words.

For example, the following shows the definition and use of a function which computes the sine of twice an angle, by multiplying whatever is on the stack by 2, and then taking the sine of the result.

     rpnfunction sin2 2 * sin
     show "expect the number 1 to follow: " {rpn 45 sin2}

The replacement words will have any synonyms in them translated first, unless they start with an underscore followed by a double backslash. Similarly, variables are substituted unless they start with an underscore.  These exceptions are to allow the use of the defined operator (rpn Mathematics).

Note: The mathematical constants e and pi are stored using rpnfunctions.  Also, two rpnfunctions are provided for finding the slope and intercept of a line joining two points, e.g.

     # Expect answers 1 and 10 ...
     show "slope=" {rpn 0 1 1 11 linear_slope}
     show "inter=" {rpn 0 1 1 11 linear_intercept}

These are useful in set grid missing above .intercept. .slope. and set z missing above .intercept. .slope..

The set commands
----------------

Set various flags and parameters which Gri will use in later commands.

set axes style
..............

     set axes style .style.     \
       | {offset [.dist_cm.]} \
       | rectangular|none|default

Tell Gri how you want the axes to look, when they are drawn later.

  * set axes style 0 Set axes to be rectangular, with an x-y axis frame labelled at the left and bottom and tic marks on all axes.

  * set axes style 1 As style 0, but only put tics on the lower and left axes.

  * set axes style 2 As style 0 but without labels or tics on any axis, i.e. just an axis frame.

  * set axes style offset [.dist_cm.] Set axes so that the actual x and y axes will be drawn with a space separating them from the data area.  The space, if not set by the .distance_cm. option, will be equal to the current tic size (see set tic size).  This command can be used together with any other set axes style command.  It applies to both the draw axes command and with any draw x|y axis command in which the axis location is not explicitly given.

  * set axes style rectangular Set axes to be rectangular, with an x-y axes frame labelled at the left and bottom.

  * set axes style none Tell gri not to bother drawing axes before drawing curves, etc.

  * set axes style default Same as set axes style 0, and with offset turned off.

set arrow size
..............

     `set arrow size .size.           \
       | {as .num. percent of length} \
       | default'

Set the arrowsize (which is stored in the builtin variable ..arrowsize..).

  * set arrow size .size. Set the arrow size (ie, half-width of the arrowhead) to .size. centimetres.

  * set arrow size as .num. percent of length Set the arrow size to be the indicated percentage of arrow length, as in "HWP" in the singles ads.  (As a flag to this, ..arrowsize.. is set to the negative of the fractional size measured in percent.)

  * set arrow size default Set the arrow size to the default of 0.2 cm.

set arrow type
..............

     set arrow type .which.

Set type of arrow, according to the value of .which., rounded to the nearest integer.  A rounded .which. value of 0 yields the default arrows, drawn with three line strokes.  Value 1 yields outlined arrows, sometimes used on definition sketches.  Value 2 yields filled, swept-back arrow heads.

This command uses the ``line join'' parameters that are presently active (Set Line Join).  So, by default, the arrow ends are rounded (because the default line-join parameter is 1).  To get pointy ends, first set the line join parameter to 0.

set beep
........

     `set beep on|off'

The command set beep on makes gri beep on errors and query.  set beep off (the default) turns this beeping off.

set bounding box
................

     `set bounding box .xleft. .ybottom. .xright. .ytop. [pt|cm]'

Set the PostScript bounding box for the graph to the indicated values.  The bounding box is used by some programs to determine the region of the page on which marks have been made.  For example, LaTeX uses the bounding box to decide how to position figures in documents.

Normally, the bounding box is computed automatically unless the -no_bounding_box commandline option has been specified; (Invoking Gri).  But if set bounding box is done, the automatically computed value is ignored and the given box is used instead.  Use this if Gri makes mistakes in its automatic selection of bounding box.

The coordinates of the bounding box may be specified in (1) user coordinates, as defined at the moment the command is executed, or (2) in points on the page, measured from an origin at the lower-left (72 point per inch), or (3) in centimeters on the page.  Which coordinate system is used depends on the last keyword -- use pt for points, cm for centimeters, and nothing at all for user-units.

The most common use is in points, since that is how many other application packages, e.g. LaTeX and dvips, specify the bounding box.

If the box is specified in the user units, the user units in effect at the moment of executing the set bounding box command are used.  This must be born in mind if the coordinate system is changing during the execution of the program, e.g.  if margins are changing or the x and y axes are changing.  For this reason it often makes sense to put this command at the end of the commandfile.

set clip
........

     `set clip [postscript] \
       {on [.xleft. .xright. .ybottom. .ytop.]} \
       {to curve} \
       | off'

Control clipping of following drawing commands.  Note that the commands have two styles, one of which includes the keyword postscript.  PostScript clipping does a cleaner job, but it results in larger file sizes.  Important if you are using postscript clipping, then you be sure to turn it off using set clip postscript off, instead of set clip off; otherwise Gri will get mixed up.

  * set clip on Don't plot data outside axes.

  * set clip postscript on As above, but Postscript clipping.

  * set clip on .xleft. .xright. .ybottom. .ytop. Don't plot data outside indicated box.

  * set clip postscript on .xleft. .xright. .ybottom. .ytop. As above, but Postscript clipping.

  * set clip off Plot all data, whether inside the axes or not.

  * set clip postscript off As above, but Postscript clipping.

  * set clip to curve set clip to the curve, as would be drawn by a draw curve filled command, i.e. to the polygon constructed by running along the xy points, in order, followed by a final segment from the last point back to the first point.  This is a "postscript" clip, as explained in the next item.

  * set clip postscript to curve As above, but Postscript clipping.

          draw axes
          set clip postscript on 10 20 0 1
          draw curve
          set clip postscript off

  * set clip postscript off Turn PostScript clipping off. See also set input data window.

set color
.........

     `set color \name               | \
         {rgb .red. .green. .blue.} | \
     {hsb .hue. .saturation. .brightness.}'

Set the color of the ``pen'' used for drawing lines and text.  Normally lines and text are drawn in the same color, but the text color can be specified independently if desired (Set Font Color).  This might be useful to get contour lines of one color and labels of another.  The spelling colour is also accepted.

In the set color \name style, set the drawing color to the indicated name, either from the builtin list (white, LightGray, darkslategray, black, red, brown, tan, orange, yellow, green, ForestGreen, cyan, blue, skyblue, magenta), or from a list created by read colornames.  In the latter case, if the colorname has more than one word in it, use quotes, e.g. set color "ghost white".

In the set color rgb ... style, set the individual color components as indicated.  The numbers .red., .green. and .blue. range from 0 (for no contribution of that color component to the final color) to 1 (for maximal contribution).  Values less than 0 are clipped to 0; values greater than 1 are clipped to 1.  EXAMPLES:

     set color rgb 0   0   0 # black
     set color rgb 1   1   1 # white
     set color rgb 1   0   0 # bright red
     set color rgb 0.5 0   0 # dark red (only 50 percent)
     set color rgb 0   1   0 # pure green
     set color rgb 1   1   0 # yellow: red + green

In the set color hsb ... style, set the individual color components as indicated.  The numbers .hue., .saturation. and .brightness. range from 0 to 1.  The color, represented by .hue., ranges from 0 for pure red, through 1/3 for pure green, and 2/3 for pure blue, and back to 1 again for pure red. The purity of the color, represented by .saturation., ranges from 0 (none of the hue is visible) to 1 (the maximal amount is present).  The brightness of the color, represented by .brightness., ranges from 0 (black) to 1 (maximal brigntness).  Values less than 0 are clipped to 0; values greater than 1 are clipped to 1.  EXAMPLES:

     set color hsb 0    1   1 # pure, bright red
     set color hsb 0    1 0.5 # half black, half red
     set color hsb .333 1   1 # pure, bright green

set colorname
.............

     `set colorname \name {rgb .red. .green. .blue.} \
                        | {hsb .hue. .saturation. .brightness.}'

Create a colorname with the indicated color.  The color components range from 0 to 1, and will be clipped to these values if they are outside this range.  EXAMPLE (borrowing a color from /usr/lib/X11/rgb.txt):

     set colorname peachpuff rgb 1 {rpn 218 255 / }  {rpn 185 255 / }
     draw box filled 2 2 3 3 cm

This command is akin to read colornames (Read Colornames), except that the latter uses an X11 database, so the color constituents range from 0 to 255, whereas for set colorname they range from 0 to 1.

set contour format
..................

     `set contour format \style|default'

Normally, Gri draws the numeric labels of contours using a format code called %g in the "C" language.  You may specify any other "long" format using this command.  For example, set contour format %.1f tells Gri to use one decimal place in the numbers, and also to prefer the "float" notation to the exponential notation.  set contour format default resets to the default %f format.  You may use quotes around the format if you need to, to make the item be a single word (e.g. set contour format "%.1f m/s").

set contour label for
.....................

     `set contour label for lines exceeding .x. cm'

Make it so contour lines shorter than .x. centimeters will not be labelled.

set contour label position
..........................

     `set contour label position \
       {.start_cm. .between_cm.} \
       | centered \
       | default'

By default, contour labels are drawn at the location 1 cm into the contour curve, measured from the startpoint of the contour (e.g., for contours crossing the axes frames, the label will be 1 cm from the frame), and then at a uniform distance along the contour.  By default, this uniform distance is the average dimension of the plotting area inside the axes.  If .start_cm. and .between_cm. are specified, the first label is drawn at a distance .start_cm. from the start of the contour, and thereafter at a separation of .between_cm..

If the centered option is used, then the contour labels are centered along the length of the line.

set contour labels
..................

     set contour labels rotated \
       | horizontal \
       | whiteunder \
       | nowhiteunder

The first two options control whether contour labels are rotated to line up with the contour lines, or whether they are horizontal (the default).

The second two options control whether the region under contour labels is whited out before drawing the label.  The default is whiteunder, which has the visual effect of the label having been drawn on a piece of paper and then pasted on.  This can look jarring when the material under the contour is an image.  When nowhiteunder is specified, the contour line is broken to make space for the text, but no whiting out is done.

set dash
........

     `set dash [.n.|{.dash_cm. .blank_cm. ...}|off]'

Control dash-style for following draw curve and draw line commands.

  * set dash Set to dashed line (0.4cm dashes, 0.1cm blanks).

  * set dash .n. Set to indicated pre-defined dashed line, according to table:

          .n. dash/cm blank/cm
           0        -        -   ... (Solid line)
           1      0.2      0.1
           2      0.4      0.1
           3      0.6      0.1
           4      0.8      0.1
           5      1.0      0.1
          10      w        w
          11      w        2w
          12      w        3w
          13      w        4w
          14      w        5w
          15      w        6w

     Where w is written, it indicates the current linewidth.  Thus, types 10 through 15 give square-dotted lines.

  * set dash .dash_cm. .blank_cm. .dash_cm. .blank_cm. ... Set to indicated dashed line.  The series of lengths .dash_cm. and .blank_cm. give the lengths of dash and blank portions (measured in centimeters).  Any number of dash/blank lengths may be given.  For example, set dash 0.5 0.1 0.1 0.1 looks good.

  * set dash off Turn dashing off, setting to a solid line.

set environment
...............

     `set environment'

Set environment (graylevel, axis length, etc) so that following plotting commands will make use of anything set by either a set command or by direct manipulation of builtin variables like ..xsize.., etc. NOTE: this should only be done by developers.

set error
.........

     `set error action to core dump'

Make Gri dump core when any error is found, to facilitate debugging.

set flag
........

     `set flag \name [off]'

Set the indicated flag to YES.  The name of the flag is contained in a single word, e.g. set flag dan_28sep_test.  The action of the flags may change with time and is undocumented.  This command is provided to enable selected users (e.g., the developer himself) to use test features of Gri before they are frozen into a fixed syntax and action.  The keyword off turns the indicated flag off.  NOTE: this should only be done by developers.

     FLAG         DATE     ACTION

     jinyu1       29sep94  'convert columns to grid'
                            outputs (x,y,z,z_predicted)

     emulate_gre   9jun97  'E' format on axes yields
                           scientific notation

     kelley1      17jun97  for kelley only - quit contour
                           trace if hit nonlegit

     kelley2      17jun97  for kelley only: print
                           info while contour tracing

set font color
..............

     set font color \name           | \
         {rgb .red. .green. .blue.} | \
     {hsb .hue. .saturation. .brightness.}

The syntax is the same as set color, except that this applies to text only.  By default, text is drawn in the same color as lines, so text color is changed as line color is changed (e.g. by using the set color or set graylevel commands)).  However, once set font color is used in a Gri program, the font thereafter maintains a separate color from the lines.

set font encoding
.................

     set font encoding PostscriptStandard | isolatin1

Permits one to control the so-called ``font encoding'' used in text. The default font encoding is ISO-Latin-1, which is best for English and other European languages.  To learn how to enter accents in a text editor, and for a brief overview of font encodings, (Non-English Text).

If the so-called ``Postscript Standard'' font encoding is required, this command permits changing the encoding.

Note: few users will ever need this command.  If you don't even know what ``font encoding'' is about, ignore this command!

set font size
.............

     `set font size {.size. [cm]}|default'

Set the size of the font for drawing of text.

  * set font size .size. Set font size to .size. points.  (A point is 1/72 of an inch, or 1/28 of a centimetre.)

  * set font size .size. cm Set font size to .size. centimetres.

  * set font size default Set font size to default = 12 pts.

If your figure is to be reproduced by a journal, you should check with them about the range of font size they need.  This will, of course, depend on whether your figure is reduced or enlarged during reproduction.  For example, American Geophysical Union (publishers of J. Geophysical Res.) recommends that one use fonts no smaller than 8 points.  They also recommend that the range in fontsize in a given figure not exceed 2.

set font to
...........

     `set font to \fontname'

Set font to named style.  Note that the backslash is not to be written, but here merely means that this word has several alternatives. For example, one might say set font to Courier.  The allowed fontnames are: Courier, a typewriter font (and the only monospaced font in Gri); Helvetica (the default), a sans-serif font commonly used in drafting scientific graphs; HelveticaBold, a bold version of Helvetica; Times (also called TimesRoman), a font used in most newspapers; TimesBold, a bold version of Times; Palatino (also called PalatinoRoman), similar to Times; Symbol, included for completeness, is a mathematical font in which "a" becomes $\alpha$ of the math mode, etc. For reference on these fonts see any book on PostScript.  The default font is Helvetica.

set graylevel
.............

     `set graylevel .brightness.|white|black'

Set graylevel for lines to indicated numerical value between 0=black and 1=white, or to the named color.

Note: if your diagram is to be reproduced by a journal, it is unlikely that the reproduction will be able to distinguish between any two graylevels which differ by less than 0.2.  Also, graylevels less than 0.2 may appear as pure black, while those of 0.8 or more may appear as pure white.  These guidelines are as specified by American Geophysical Union (publishers of J. Geophysical Res.), as of 1998.

set grid missing
................

General format is

     `set grid missing \
       {above|below .intercept. .slope} \
       | {inside curve}'

The style

     `set grid missing above|below .intercept. .slope'

sets grid to missing value for all points above/below the line defined by y = .intercept. + .slope. * x

The style

     `set grid missing inside curve'

sets the grid to the missing value throughout an area described by the curve last read in with read columns.  This is useful for e.g. excluding land areas while contouring ocean properties.  The curve may contain several "islands," each tracing (clockwise) a region inside of which the grid is to considered missing.  If the first point in an island doesn't match the last, then an imaginary line is assumed which connects them.  Multiple islands may be separated by missing-value codes.

See also Set Z Missing.

set ignore initial newline
..........................

     `set ignore initial newline [off]'

Make Gri ignore a newline if it occurs as the first character of the next data file.  This is used for files made by FORTRAN programs on VAX/VMS computers.

set ignore error eof
....................

     `set ignore error eof'

Stop Gri from considering that to encounter an end of file in future read commands consitutes an error; Gri will simply warn about future EOFs.

set image colorscale
....................

     set image colorscale hsb .h. .s. .b. .im_value. \
         hsb .h. .s. .b. .im_value. [increment .im_value.]
     set image colorscale rgb .r. .g. .b. .im_value. \
         rgb .r. .g. .b. .im_value. [increment .im_value.]
     set image colorscale \
       \name .im_value. \
       \name .im_value. \
       [increment .im_value.]

Set colorscale mapping for image, using HSB (hue, saturation, brightness) specification, RGB (red, green, blue) color specification, or named colors.  The image range must previously have been set by set image range, so that the .im_value. values will have meaning.  Two pairs of (color, image-value) are given, and possibly an increment.  Normally the colors are smoothly blended between the endpoints, but if an increment is supplied, the colors are quantized. The HSB method allows creation of spectral palettes, while the other two methods create simple blending between the two endpoints.

EG: To get a spectrum ranging between pure red (H=0) for image value of -10.0, and pure blue (H=2/3) for image value of 10.0, do this:

     set image colorscale hsb 0 1 1 -10 hsb .666 1 1 10

EG: To get a scale running from pure red (at image-value 10.0) into pure blue (at image-value 25.1), but with the colors blending intuitively in between (i.e., blending as paint might), use rgb color specification, as follows:

     set image colorscale rgb 1 0 0 10 rgb  0 0 1 25.1

EG: To get a quantized blend between the X11 colors skyblue at image value of 0 and tan at image value of 20, and with steps at image values incrementing by 5, do this:

     set image colorscale skyblue 0 tan 20 increment 5

Note that the traversal is through RGB space, so it is intuitive, not spectral.  See set color for a list of X11 colors known to Gri.

See also read image colorscale (Read Image Colorscale).

set image grayscale
...................

     `set image grayscale using histogram \
       [black .bl. white .wh.]'

     `set image grayscale \
       [black .bl. white .wh. [increment .inc.]]'

Set up a grayscale mapping for images.  The image range must have previously have been set by set image range.

     `set image grayscale using histogram [black .bl. white .wh.]'

Create a grayscale mapping using linearized cumulative histogram enhancement.  The image range must have previously have been set by set image range.

This creates maximal contrast in each range of graylevels, and is useful for tracing subtle features between different images (for example, it makes it easier to trace fronts between successive satellite images).  The entire histogram is expanded, from the smallest value in the image to the largest.

With no options specified, the histogram is done from 0 in the image to 255 in the image.  If the black/white options are specified, the histogram is done between these values.

     `set image grayscale \
       [black .bl. white .wh. [increment .inc.]]'

With no optional parameters, create a grayscale mapping for the current image, scaling it from black for the mininum value in the image to white for the maximum value.  The image range must have previously have been set by set image range.

The optional parameters .wh. and .bl. specify the values to be drawn in white and black in the image, with smooth linear blending in between.

Normally the blending from white to black is smooth (linear), but if the additional optional parameter .inc. is specified, the blending is quantized, jumping to darker values at (.wh. + .inc.), (.wh. + 2* .inc.), etc.  (The sign of .inc. will be altered, if necessary, to ensure that (.wh. + .inc.) is between .wh. and .inc..)  The colour switches to pure white at the value .wh., and remains pure white everywhere on the "white" side of this value.  Similarly, the transition to pure black occurs at the value .bl..  In other words, neither pure white nor pure black is present inside the interval from .wh. to .bl..  Therefore, when using the draw image palette command, you might want to extend the range by one increment so as to get an example of both pure white and pure black.

     .w. = 0
     .b. = 1
     .i. = 0.2
     set image grayscale white .w. black .b. increment .i.
     draw image palette left \
       {rpn .w. .i. -} \
       right {rpn .b. .i. +} \
       increment .i.

set image missing value color
.............................

     set image missing value color to white|black|\
         {graylevel .brightness.}|{rgb .r. .g. .b.}

Set the color of ``missing'' pixels (white by default).  The image range must have previously have been set by set image range.  Pixels with missing values can result from creating images from grids which have missing values; see the convert grid to image command.  The .brightness. parameter in the graylevel style ranges from 0 for black to 1 for white.  The rgb parameters allow setting to full color.

set image range
...............

     set image range .0value. .255value.

Specify maximum possible range of values that images can hold, in user units.  Gri needs to know this because it stores images in a limited format capable of holding only 256 distinct values.  Unlike some other programs, Gri encourages (forces) the user to specify things in terms of user-units, not image-units.  This has the advantage of working regardless of the number of bits per pixel.  Thus, for example, set image grayscale, set image colorscale, draw image grayscale, etc, all use user units.

When an image is created by convert grid to image, values outside the range spanned by .0value. and .255value. are clipped. (There is no need, however, for .0value. to be less than .255value..)  This clipping discards information, so make sure the range you give is larger than the range of data in the grid.

EXAMPLE: consider a satellite image in which an internal value of 0 is meant to correspond to 0 degrees Celsius, and an internal value of 255 corresponds to 25.5 degrees.  (This is a common scale.)  Then the Gri command set image range 0 25.5 would establish the required range.  If this range were combined with a linear grayscale mapping (see set image grayscale), the resultant granularity in the internal representation of the user values would be (25.5-0)/255 or 0.1 degrees Celsius; temperature variations from pixel to pixel which were less than 0.1 degrees would be lost.

All other image commands require that the range has been set. Thus, all these commands fail unless set image range has been done: draw image, draw image palette, read image, convert grid to image, set image grayscale, and set image colorscale.

NOTE: If a range already exists when set image range is used, then the settings are altered.  Thoughtless usage can therefore lead to confusing results.  (The situation is like setting an axis scale, plotting a curve with no axes, then altering the scale and plotting the new axes.  It is legal but not necessarily smart.)

set input data window
.....................

     `set input data window x|y {.min. .max.}|off'

Create a data window for following read statements.

  * set input data window x .min. .max. For future reading commands, ignore all data with x less than .min. or x greater than .max. The data not in the interval will not be read in at all.  This will hold until set data window x off is done, in which case all data will be read in.

  * set input data window x off Return to normal conditions, in which all data are read in.

  * set input data window y .min. .max. Analgous to command for x.

  * set input data window y off Analagous to command for x.

EXAMPLE: To set the input data window as the current x axis plus a border of 5 centimetres to left and right, do the following:

     set input data window x \
       {rpn ..xleft..  xusertocm 5 - xcmtouser} \
       {rpn ..xright.. xusertocm 5 + xcmtouser}

See also set clip

set input data separator
........................

     `set input data separator TAB|default'

Set the separator between data items.  The default method is to assume that data items are separated by one or more spaces or tabs, and also to ignore any spaces or tabs at the start of a data line.

In the TAB method the data are assumed to be separated by a SINGLE tab character.  (Multiple tabs will result in null values being assigned to items -- almost certainly not what you want!)  Also, initial spaces and tabs on lines are NOT skipped.

Use the TAB method only after thinking carefully about the above, since the assignment of null values is problematic.

set line cap
............

     `set line cap .type.'

Set the type of ends (caps) of lines.  Use .type. of value 0 for square ends, cut off precisely at the end of line, or 1 for round ends which overhang half the line width, or 2 for square ends which overhang half the line width.  The selected style is used for the ends of line segments, as well as at corners.  In PostScript parlance, therefore, this command sets both the linecap and the linejoin parameters.

This command only applies to lines drawn with draw curve, draw line and draw polygon.  Axes are always drawn with a line cap of 0.

set line join
.............

     `set line join .type.'

Set the type of intersection of lines.  Use .type. of value 0 for mitered joins (pointy ends that may extend beyond the data points), a value of 1 for rounded ends (the default), or a value of 2 for bevelled (squared-off) ends.  See the setlinejoin command in any text on the PostScript language for more information.

This command only applies to lines drawn with draw curve, draw line and draw polygon.  Axes are always drawn with a line join of 0.

set line width
..............

     `set line width \
       [axis|symbol|all] \
       .width_pt. \
       | {rapidograph \name} \
       | default'

Set the width of lines used to draw curves (default), axes, symbols, or all of the above.  The width may be set to a value specified in points (conversion: 72 pt = 1 inch), to a named rapidograph width, or to the default value.  The initial default values are: 0.709pt (or rapidograph 3x0) for curves; 0.369pt (or rapidograph 6x0) for axes; 0.369pt (or rapidograph 6x0) for symbols.  (To learn more about standard pen widths, see the ISO 9175-1 documents.)

If your figure is to be reproduced by a journal, you should check with them about the range of line thicknesses they recommend.  This will, of course, depend on whether your figure is reduced or enlarged during reproduction.  For example, American Geophysical Union (publishers of J. Geophysical Res.) recommends that one use line thicknesses no less than 0.5 points and no more than 4 points.

The rapidograph settings match the standard set of widths used in technical fountain pens.  The table below gives width names along with the width in points and centimetres, as given in the specifications supplied with Rapidograph technical fountain pens.  Names marked by the symbol * are in sequence increasing by the factor root(2).  Texts on technical drawing often suggest using linewidths in the ratio of 2 or root(2).  On many printers, the variation in width from root(2) increase is too subtle to see, so the factor-of-2 rule may be preferable.  To get sizes in a sequence doubling in width, pick from the list (6x0, 3x0, 1, 3.5 7).  To get a sequence increasing in width by root(2), pick from the list (6x0, 4x0, 3x0, 0, 1, 2.5, 3.5, 6, 7).  The eye can distinguish curves with linewidths differing by a factor of root(2) if the image is of high quality, but a factor of 2 is usually better.  Similarly, for overhead projections and projected slides, one would do well to use linewidths differing by a factor of 4.

This is the list of rapidograph linewidths:

       Name      pt    cm
       ====    =====  =====
     *  6x0    0.369  0.013
     *  4x0    0.510  0.018
     *  3x0    0.709  0.025
         00    0.850  0.03
     *    0    0.992  0.035
     *    1    1.417  0.05
          2    1.701  0.06
     *    2.5  1.984  0.07
          3    2.268  0.08
     *    3.5  2.835  0.1
          4    3.402  0.12
     *    6    3.969  0.14
     *    7    5.669  0.2

set missing value
.................

     `set missing value .value.|none'

If a numerical value is given, set the missing-value code to that value, and also store this value in the builtin variable ..missingvalue.. and the builtin synonym \.missingvalue.. also.  After this command, Gri will ignore any data that are within 0.1 percent of this value.  (This feature is commonly used in geophysical data.)

If none is given, turn off this feature.

The default is that the feature is turned off.

set page size
.............

     `set page size letter|legal|folio|tabloid|A0|A1|A2|A3|A4|A5'

Set the page dimension, as indicated below.

letter
     American "letter" size: 8.5 x 11 inches

legal
     American "legal" size: 8.5 x 14 inches

folio
     American "folio" size: 8.5 x 13 inches

tabloid
     American "tabloid" size: 11 x 17 inches

A5
     Metric size: 14.8 x 21.0 cm

A4
     Metric size: 21.0 x 29.7 cm

A3
     Metric size: 29.7 x 42.0 cm

A2
     Metric size: 42.0 x 59.4 cm

A1
     Metric size: 59.4 x 84.1 cm

A0
     Metric size: 84.1 x 118.9 cm

The effect is to possibly alter the PostScript "bounding box."  If all the drawn material fits within the indicated page, then the bounding box is not altered.  (In other words, Gri will still keep the bounding box tight on the drawn items.)

However, if any drawn item extends beyond the indicated size, it will be clipped to the boundary.

set page
........

     `set page portrait \
       | landscape \
       | {factor .mag.} \
       | {translate .xcm. .ycm.}'

Control orientation or scaling of what is drawn on the paper.

  * set page portrait Print graph normally (default).

  * set page landscape Print graph sideways.

  * set page factor .mag. Scale everything to be drawn on the paper by the indicated magnification factor.  This must be called before any drawing commands.

  * set page translate .xcm. .ycm. Translate everything to be drawn on the paper by the indicated x/y distances.  This must be called before any drawing commands.

Note: The order of the factor/translate commands matters, so you may need to experiment.  For example,

     set page translate 2 1
     set page factor 0.5

moves anything that would have been drawn at the lower-left corner of the paper onto the point 2cm from the left side and 1cm from the bottom side of the paper, and then applies the multiplication factor. Reversing the order gives quite different results.  PostScript gurus should note that the following two commands are inserted into the PostScript file:

     56.900000 28.450000 translate
     0.500000 0.500000 scale

set panel
.........

     set panel .row. .col.

Establish the geometry for the panel in the indicated row and column; that is, select which defined panel to draw into.  The bottom row has .row. = 1, and the leftmost column has .col. = 1.  This must be used only after defining the panel layout using Panels .row. .col. .dx_cm. .dy_cm..

set panels
..........

     set panels .rows. .cols. [.dx_cm. .dy_cm.]

Set up for multipanel plots, with spacing .dx_cm. between the columns and .dy_cm. between the rows.  If the spacings are not supplied, 2cm is used.  The panels fill the rectangle which would otherwise contain the single axis frame, as set by set x size and set x margin, etc.

The global variables .panel_dx., .panel_dy., .panel_xmargin., .panel_ymargin., .panel_xsize., and .panel_ysize are created, to be used by later calls to set panel.

EXAMPLE

     # Draw 2 panels across, 3 up the page.

     # The Panel interiors will be in region cornered
     # by (2,2), (12,22) cm
     set x margin 2
     set y margin 2
     set x size 10
     set y size 20
     set panels 2 3

     # Create dummy scale
     set x axis 0 1
     set y axis 0 1

     # Draw blank axes
     et panel 1 1
     raw axes
     set panel 1 2
     draw axes
     set panel 1 3
     draw axes
     set panel 2 1
     draw axes
     set panel 2 2
     draw axes
     set panel 2 3
     draw axes

See also set panel .row. .col.

set path
........

     set path to "\path"|default for data|commands

Set the directory path that open will search for data files, or that insert will search for command files.  This search will not be done if the filename starts with a /, ~, or . character.

The path is formatted in a colon-separated manner, following the normal Unix convention, and searching is from left to right.  For example, the path ".:/usr/lib/gri" tells Gri to search for the file first in the local directory (named .), and if it is not found there, to look next in the directory named /usr/lib/gri.

The indicated path is stored in either \.path_data. or \.path_commands., as appropriate.  At startup time, each of these paths is set to ".", the current directory, and this value is reset if the default keyword is provided to this command.

If you need to know where the file was eventually found, save the \.return_value. just after the open command was executed. For example, the following defines the synonym \uk, which is the full pathname of the file containing some sort of data about Great Britain.

     set path to "/atlases/world:/atlases/northern_hemisphere" for data
     open britain.dat        # we don't know where file is ...
     \gb = "\.return_value." # ... until now!

     # Can later do command such as
     #    read from \gb
     # or
     #    rewind \gb
     # to work with this particular file, even if
     # there is another file open that also is
     # named "britain.dat".

set postscript filename
.......................

     `set postscript filename "\name"'

Set name of PostScript file, over-riding the present name.

set symbol size
...............

     `set symbol size .diameter_cm.|default'

Control the diameter of symbols drawn by draw symbol command.

  * set symbol size .diameter_cm. Make symbol size be .diameter_cm. centimeters in diameter.

  * set symbol size default Set to default diameter of 0.1 cm.

set tic size
............

     `set tic size .size.|default'

Control size of tics on axes.

  * set tic size .size. Set tic size to .size. centimetres.

  * set tic size default Set tic size to default of 0.2 cm.

  * set tics in|out Make axis tics point inward or outward.  The default is outward.

set trace
.........

     `set trace [on|off]'

Control printing of command lines as they are processed.

  * set trace Make Gri print command lines as they are processed.

  * set trace on Same as set trace.

  * set trace off Prevent printing command lines (default).

set transparency
................

     `set transparency .transparency.'

Set the transparency of drawn items, 0 for opaque and 1 for invisibly faint.  This command is provisional, as of summer 2004, and this part of the documentation needs to be fleshed out so users can build intuition on transparency.  For example, a quick quiz: what color do you think comes from drawing red on top of yellow, or on top of blue?

set u scale
...........

     `set u scale .cm_per_unit.|{as x}'

Set scale for x-component of arrows.

  * set u scale .cm_per_unit. Set scale for u component of arrows.

  * set u scale as x Set scale for u component of arrows to be the same as the x-scale. Equivalent to set u scale as {rpn ..xsize.. ..xright.. ..xleft.. - /}.

NOTE: this only works if the x-scale is LINEAR (see set x type).

set v scale
...........

     `set v scale .cm_per_unit.|{as y}'

Set scale for y-component of arrows.

  * set v scale .cm_per_unit. Set scale for v component of arrows.

  * set v scale as y Set scale for v component of arrows to be the same as the y-scale. Equivalent to set v scale as {rpn ..ysize.. ..ytop.. ..ybottom.. - /}.

NOTE: this only works if the y-scale is LINEAR (see set y type).

set x axis
..........

     `set x axis top'
     `set x axis bottom'
     `set x axis increasing'
     `set x axis decreasing'
     `set x axis unknown'
     `set x axis .left. .right. [.incBig. [.incSml.]] [labelling .labelling_value.]'
     `set x axis labels [add] .position_1. "label_1" [.position_2. "label_2" [...]]'
     `set x axis labels automatic'

Control various things about the x axis.

  * set x axis top Make next x-axis to be drawn have labels above the axis.

  * set x axis bottom Make next x-axis to be drawn have labels below the axis.

  * set x axis increasing Make next x-axis to be drawn have numeric labels increasing to the right.  This applies only if autoscaling is done; otherwise, the supplied values (.left. .right. [.incBig.  [.incSml.]]) are used.

  * set x axis decreasing Make next x-axis to be drawn have numeric labels decreasing to the right.  This applies only if autoscaling is done; otherwise, the supplied values (.left. .right. [.incBig.  [.incSml.]]) are used.

  * set x axis unknown Make Gri forget any existing scale for the x axis, whether set by another set x axis command or automatically, during reading of data.  This is essentially a synonym for delete x scale.

  * set x axis .left. .right. Make x-axis range from .left. to .right.

  * set x axis .left. .right. .incBig. Make x-axis range from .left. to .right., with labelled increments at .incBig. Note: In the case of log axes, and provided that set x type log has been called previously, the .incBig. parameter has a different meaning: it is the interval, in decades, between numbered labels; the default is 1.

  * set x axis .left. .right. .incBig. labelling .labelling_value. As above, but with the axis labels including the indicated value, and incremented larger and smaller by .incBig.  (This does not work for logarithmic axes.)

  * set x axis .left .right. .incBig. .incSml. Make x-axis range from .left. to .right., with labelled increments at .incBig., and small tics at .incSml.  NOTE: if the axis is logarithmic, the value of .incSml. takes on a special meaning: if it is positive then small tics are put at values 2, 3, 4, etc. between the decades, but if .incSml. is negative then no such small tics are used.

  * set x axis .left .right. .incBig. .incSml. labelling .labelling_value. As above, but with the axis labels including the indicated value, and incremented larger and smaller by .incBig. (This does not work for logarithmic axes.)

  * set x axis labels .position. "label" [.position. "label" [...]] Override the automatic labelling at axis tics, and instead put the indicated labels at the indicated x values.  For example, a day-of-week axis can be created by the code:

          set x axis 0 7 1
          set x axis labels 0.5 "Mon" 1.5 "Tue" 2.5 "Wed" \
                            3.5 "Thu" 4.5 "Fri" 5.5 "Sat" \
                            6.5 "Sun"

     The command replaces any existing labels, unless the `add' keyword is present, in which case the new label information is appended to any existing information.

  * set x axis labels automatic Return to automatically-generated axis labels, undoing the command of the previous item.

set x format
............

     `set x format \format|default|off

Set format for numbers on x axis.  The format is specified in the manner of the "C" programming language.  The C formats (i.e., %f, %e and %g) are permitted. For example, set x format %.1f tells Gri to use 1 decimal place, and to prefer the "float" notation to the exponential notation.  The form set x format off tells Gri not to write numbers on the axis. To get spaces in your format, enclose the format string in double-quotes, e.g., you might use set x format "%.0f$\circ$ W" for a map, or set x format "%f " to make the numbers appear to the left of their normal location.

The default format is %lg.

set x grid
..........

     `set x grid .left. .right. .inc.|{/.cols.}'

Create x-grid for contour or image.  If a grid already exists, an error will be declared; the way to interpolate from an existing grid to a new one is with the interpolate x grid command.

  * set x grid .left. .right. .inc. Create x-grid ranging from the value .left. at the left to .right. at the right, stepping by an increment of .inc..

  * set x grid .left. .right. /.cols. Create x-grid with .cols. points, ranging from the value .left. at the left to .right. at the right.

set x margin
............

     `set x margin {[bigger|smaller] .size.}|default'

Control x margin, that is, the space between the left-hand side of the page and the left-hand side of the plotting area.  (Note that axis labels are drawn inside the margin; the margin extends to the axis line, not to the labels.)

  * set x margin .size. Set left margin to .size. cm.  It is permissible to have negative margins, with the expected effect.

  * set x margin bigger .size. Increases left margin by .size. cm.

  * set x margin smaller .size. Decreases left margin by .size. cm.

  * set x margin default Set left margin to default = 6 cm.

set x name
..........

     `set x name "\name"|default'

Set name of x-axis to the indicated string.  An empty string (set x name "") causes the x axis to be unlabelled.  The default is "x".

set x size
..........

     `set x size .width_cm.|default'

Set the width of the plotting area.  This does not include axis labels, only the interior part of the plot.

  * set x size .width_cm. Set width of x-axis in centimeters.

  * set x size default Set width of x-axis to default = 10 cm.

set x type
..........

     set x type linear|log|{map E|W|N|S}

Control transformation function mapping user units to centimetres on the page.

  * set x type linear Set to linear axis.

  * set x type log Set to log axis.  To avoid clashes in the linear to log transform, this command should precede the creation of an axis scale, either explicitly through the set x axis .left. .right. ... command or implicitly through the read columns command.

  * set x type map E|W|N|S Set to be a map.  This means that whole numbers on the axis will have a degree sign written after them (and then the letter E, etc) and that numbers which are multiples of 1/60 will be written in degree-minute format, and that similarly numbers which are divisible by 1/3600 will be in degree-minute-second format.  If none of these things apply, the axis labels will be written in decimal degrees.  Note that this command overrides any format set by set x format.

     BUG: this only has an effect if the axis is not already of type log.

set y axis
..........

     `set y axis left'
     `set y axis right'
     `set y axis increasing'
     `set y axis decreasing'
     `set y axis .bottom. .top. [.incBig. [.incSml.]] [labelling .labelling_value.]'
     `set y axis labels [add] .position_1. "label_1" [.position_2. "label_2" [...]]'
     `set y axis labels automatic'

Control various things about the y axis.

  * set y axis name horizontal Make y-axis name be horizontal.

  * set y axis name vertical Make y-axis name be vertical (default).

  * set y axis left Make next y-axis to be drawn have labels to the left of the axis.

  * set y axis right Make next y-axis to be drawn have labels to the right of the axis.

  * set y axis increasing Make next y-axis to be drawn have numeric labels increasing up the page. This applies only if autoscaling is done; otherwise, the supplied values (.left. .right. [.incBig.  [.incSml.]]) are used.

  * set y axis decreasing Make next y-axis to be drawn have numeric labels decreasing up the page. This applies only if autoscaling is done; otherwise, the supplied values (.left. .right. [.incBig.  [.incSml.]]) are used.

  * set y axis unknown Make Gri forget any existing scale for the y axis, whether set by another set y axis command or automatically, during reading of data.  This is essentially a synonym for delete y scale.

  * set y axis .bottom. .top. Make y-axis range from .bottom. to .top.

  * set y axis .bottom. .top. .incBig. Make y-axis range from .bottom. to .top., with labelled increments at .incBig.

  * set y axis .bottom. .top. .incBig. labelling .labelling_value. As above, but with the axis labels including the indicated value, and incremented larger and smaller by .incBig. (This does not work for logarithmic axes.)

  * set y axis .bottom. .top. .incBig. .incSml. Make y-axis range from .bottom. to .top., with labelled increments at .incBig., and small tics at .incSml.  NOTE: if the axis is logarithmic, the value of .incSml. takes on a special meaning: if it is positive then small tics are put at values 2, 3, 4, etc. between the decades, but if .incSml. is negative then no such small tics are used.

  * set y axis .bottom. .top. .incBig. .incSml. labelling .labelling_value. As above, but with the axis labels including the indicated value, and incremented larger and smaller by .incBig. (This does not work for logarithmic axes.)

  * set y axis labels .position. "label" [.position. "label" [...]] Override the automatic labelling at axis tics, and instead put the indicated labels at the indicated y values.  For example, a physical-condition axis can be created by the code:

          set y axis 0 1 0.5
          set y axis labels 0.25 "Weak" 0.75 "Strong"

     The command replaces any existing labels, unless the `add' keyword is present, in which case the new label information is appended to any existing information.

  * set y axis labels automatic Return to automatically-generated axis labels, undoing the command of the previous item.

  * set y axis name vertical Cause future y axes to be drawn with the name aligned vertically (the default).

  * set y axis name horizontal Cause future y axes to be drawn with the name aligned horizontally.

set y format
............

     `set y format \format|default|off'

Set format for numbers on y axis.  The format is specified in the manner of the "C" programming language.  The C formats (i.e., %f, %e and %lg) are permitted.  For example, set y format %.1f tells Gri to use 1 decimal place, and to prefer the "float" notation to the exponential notation. The form set y format off tells Gri not to write numbers on the axis.  To get spaces in your format, enclose the format string in double-quotes, e.g., you might use set y format "%.0f$\circ$ N" for a map, or set y format "%f" to make the numbers appear to the right of their normal location.

The default format is %lg.

set y grid
..........

     `set y grid .bottom. .top. .inc.|{/.rows.}'

Create y-grid for contour or image.  If a grid already exists, an error will be declared; the way to interpolate from an existing grid to a new one is with the interpolate x grid command.

  * set y grid .bottom. .top. .inc. Create y-grid ranging from the value .bottom. at the bottom to .top. at the top, stepping by an increment of .inc..

  * set y grid .bottom. .top. /.rows. Create y-grid with .rows. points, ranging from the value .bottom. at the bottom to .top. at the top.

set y margin
............

     `set y margin {[bigger|smaller] .size.}|default'

Control y margin, that is, the space between the bottom side of the page and the bottom of the plotting area.  (Note that axis labels are drawn inside the margin; the margin extends to the axis line, not to the labels.)

  * set y margin .size. Set bottom margin to .size. centimeters.  It is permissible to have negative margins, with the expected effect.

  * set y margin bigger .size. Increases bottom margin by .size. centimeters.

  * set y margin smaller .size. Decreases bottom margin by .size. centimeters.

  * set y margin default Set bottom margin to default = 6 cm.

set y name
..........

     `set y name "\name"|default'

Set name of y-axis to the indicated string.  An empty string (set y name "") causes the x axis to be unlabelled.  The default is "y".

set y size
..........

     `set y size .height_cm.|default'

Set the width of the plotting area.  This does not include axis labels, only the interior part of the plot.

  * set y size .height_cm. Set height of y-axis in centimeters.

  * set y size default Set width of y-axis to default = 10 cm.

set y type
..........

     set y type linear|log|{map N|S|E|W}

Control transformation function mapping user units to centimetres on the page.

  * set y type linear Set to linear axis.

  * set y type log Set to log axis.  To avoid clashes in the linear to log transform, this command should precede the creation of an axis scale, either explicitly through the set y axis .left. .right. ... command or implicitly through the read columns command.

  * set y type map N|S|E|W Set to be a map.  This means that whole numbers on the axis will have a degree sign written after them (and then the letter N, etc), and that numbers which are multiples of 1/60 will be written in degree-minute format, and that similarly numbers which are divisible by 1/3600 will be in degree-minute-second format.  If none of these things apply, the axis labels will be written in decimal degrees.  Note that this command overrides any format set by set y format.

     BUG: this only has an effect if the axis is not already of type log.

set z missing
.............

     set z missing above|below .intercept. .slope.

Set z column to be missing whenever the associated y and x columns are above/below the line defined by y = .intercept. + .slope. * x

show
----

     `show ...'

Show some information by printing it to standard output.

  * show all Show lots of information about plot.

  * show axes Show information about axes.

  * show color Show the current pen color used for lines and text.  This is not to be confused with image color, which is independent.

  * show colornames Show all colors known by name, as defined by read colornames command and also the builtin colors defined automatically (e.g. white, black, red, etc), (Read Colornames).

  * show columns Show x, y, z, u, v column data.

  * show columns statistics Show means, std devs, etc for columns.

  * show flags Show values of all flags. (Developers only.)

  * show grid Show an indication of the grid data (used for contouring).

  * show grid mask Show 1 if grid data are valid or 0 if contours will not extend into this region.

  * show image Show information about image, such as a histogram of values, and, if the image is small enough, the actual data.

  * show license Show the license for Gri, which outlines how users are allowed to share it freely.

  * show misc Show miscellaneous information about the plot, the data, etc.

  * show next line Show next line of data-file.

  * show synonyms Show values of all synonyms, whether built-in or user-defined.

  * show stopwatch Show elapsed time since first call to this command in the given Gri program.

  * show time Show the current time.

  * show traceback Show traceback (i.e., the tree of commands being done at this instant).

  * show variables Show values of all variables, whether built-in or user-defined.

  * show .value. Show value of indicated variable.

  * show {rpn ...} Show result of computing indicated expression.

  * show "some text" Print the indicated string.  You may use a double-slash to prevent Gri from substituting synonym values; thus it is common to do e.g.

          \var = "Temperature"
          show "Plotting \\var = 'var'"

     which will produce the output line

          Plotting \\var = 'Temperature'

  * show "time=" .time. "; depth=" .depth. Print strings and values as indicated.  If the last item is ellipses (three dots with no spaces between them), then no newline is printed; this makes the next show statement print on the same line.

     To get a newline in a printed string, use the three-character glyph \<<, and to get a horizontal tab, use \>>, as in the examples below

          \a = "HI"
          show "\\a=\a"
          system echo -e "a\\nb"
          show "first line\<<second line"
          show "first line\<<\>>(tabbed) second line"
          show "first line\<<\>>(tabbed) second line"

skip
----

     `skip [forward|backward] [.n.]'

  * skip For ascii files, skip next line in the data file.  For binary files, skip forward 1 byte.

  * skip backward For ascii files, skip backward 1 line in the data file.  For binary files, skip backward 1 byte.

  * skip .n. or forward .n. For ascii files, skip forward .n. lines in the data file.  For binary files, skip forward .n. bytes.

  * skip backward .n. For ascii files, skip backward .n. lines in the data file.  For binary files, skip backward .n. bytes.

sleep
-----

     `sleep .sec.'

Cause Gri to sleep for the indicated number of seconds, which should be a positive integer.  This command is ignored if .sec. is zero or negative, and the value of .sec. is first rounded to the nearest integer.

Normally, this command is used only by the developer, as a way to slow down Gri execution, to allow easier monitoring for debugging purposes. Beware: it is tricky to kill a sleeping job!

smooth
------

All these smoothing commands ignore the location of the data.  For equispaced data these algorithms have the standard interpretation in terms of digital filters.  For non-equispaced data, the interpretation is up to the user.

     `smooth {x [.n.]} \
       | {y [.n.]} \
       | {grid data [.f.|{along x|y}]}'

The smooth x command does smoothing by the following formula

     x[i-1]   x[i]   x[i+1]
     ------ + ---- + ------
       4       2       4

The smooth x .n. command does boxcar smoothing with centred boxcars .n. points wide.  The smooth y command does the same as smooth x, but on the y column.

There are several methods of smoothing grid data.  Note that isolated missing values are filled in by each method.  (Let the author know if you'd like that `feature' to be an option.)

The smooth grid data command smooths gridded data, by weighted average in a plus-shaped window about each gridpoint.  The smoothing algorithm replaces each interior gridpoint value z[i][j] by

     z[i][j]   z[i-1][j] + z[i+1][j] + z[i][j-1] + z[i][j+1]
     ------- + ---------------------------------------------
        2                          8

Points along the edges are smoothed by the same formula, after inventing image points outside the domain by planar extrapolation.

The smooth grid data .f. command performs partial smoothing.  A temporary fully-smoothed grid zSMOOTH[i][h] is constructed as above, and a linear combination of this grid and the original grid is used as the replacement grid:

     z[i][j] = (1-f) * z[i][j] + f * zSMOOTH[i][j]

where f is the value indicated on the command line. Thus, smooth grid data 0 performs no smoothing at all, while smooth grid data 1 is equivalent to smooth grid data.

The smooth grid data along x command smooths the grid data across x (i.e., horizontally), by replacing each value z[i][j] with the value

     z[i][j]   z[i-1][j] + z[i+1][j]
     ------- + ---------------------
        2                4

Points along the edges are smoothed by the same formula, after inventing image points outside the domain by linear extrapolation.

The smooth grid data along y command does the same thing as smooth grid data along x, but the smoothing is along y.

See also Filter, a generalization of smooth x|y which allows for more sophisticated filters.

source
------

     `source \filename'

Perform the commands in the indicated file.

If the file cannot be found, an error results.  Contrast this with the insert command (Insert), which has the ability to search for the file through a user-specified path (Set Path To).

sprintf
-------

     `sprintf \synonym "format" .variable. [.variable. [...]]'

Write numbers into a synonym (text string).  This is useful for labelling plots.

sprintf \out "a = %lf b = %.2f" .a. .b. - Create a synonym called \out, and print the values of the variables .a. and .b. into it.  If .a. = 1 and .b. = 0.112, then \out will be "a = 1 b = 0.11"

Formatting codes are as in the C programming language, eg:

     %.2f  -- Use floating point with 2 decimal places.
     %9.2f -- As above, but number takes 9 characters.
     %e    -- Use exponential notation.

CAUTION: Variables are stored in the floating point in Gri, so you must use a format like "%f", not an integer code like "%d". If you want an integer, use "%.0f".

state
-----

     `state save|restore|display'

The save operation pushes a record of the graphics state (pen and font characteristics, margins, axis lengths, min/max/inc values on axes, etc) onto a stack.  The restore operation replaces the present state with whatever is on top of the stack, and then pops the stack. Use display to see some of the state properties.

The state command is useful for temporary changes of axis properties, etc.

BUG: only line characteristics (width, color) and font characteristics (font, size, color) are saved so far.  In fact, the full list of what should be saved has not yet been finalized by the author.

superuser
---------

     `superuser [value]'

Allow extra debugging information and commands.  Normally, this command and the corresponding commandline flag -superuser are only used by programmers altering the Gri source.

These are the flags and their meanings:

  * 1 Print cmdline before/after substituting synonyms.

  * 2 Print cmdline before/after substituting rpn expressions.

  * 4 Print all new commands as they are being defined

  * 8 Print the system commands that are used with open "...|" and in other instances.

  * 128 Changeable; only author should use this.

  * 256 Changeable; only author should use this.

Note that all flags are equal to 2 raised to an integer power.  Since the flag values are detected by a bitwise OR, you can combine flags by adding; thus specifying a flag of 5 yields flags 1 and 4 together; specifying 15 yields flags 1, 2, 4 and 8.

system
------

     `system \system-command'

Tell the operating system to perform the indicated action.  Whatever string follows the word system is passed directly to the operating system, after substitution of synonyms if any exist.

If your system command contains double-slashes, you must protect them from Gri (which will interpret them as comments) by enclosing in double-quotes, e.g. system cat A | sed -e "s/foo//g" | cat > B. (In the particular case of the sed command you could also do system cat A | sed -e "s:foo::g" | cat > B.

Note that rpn expressions are not evaluated, and variable values are not substituted before passing the string to the operating system. The exit status is stored in the builtin variable ..exit_status...

There are two ways to use the system:

  * Assign output to synonym: The form \synonym = system ... does the system command and then inserts the output from that command into the indicated synonym.)

  * Just run a command: The command system ls will list the files in the current directory.

For long commands, there are two approaches, the second preferred:

  * Use continuation lines: String a lot of information onto one effective system line, using the \ line-continuation character at the ends of lines.  The problem is that it is very easy to lose one of these backslashes.  The next method is better.

  * Here-is syntax The here-is syntax of many unix shells is also provided.  If the system command contains the characters << followed by a word (with no space between!) then Gri will issue a system command which includes not only this line but also all succeeding lines, until a line is found which matches the indicated word precisely (with no leading space allowed).  The << "WORD" syntax is also supported, meaning that the operating system is being told not to mess with the dollar-signs -- needed in perl.

     Be careful using this inside a new-command.  Gri Recognizes the end of the body of a new-command by a line with } in the first column, and no non-white characters thereafter. If you system command happens to use a line with a curly brace (as in a loop in perl, for example), you must put whitespace before the brace. This won't affect the system command, but it will let Gri correctly realize that this is not the end of the new-command.  For more information on new-commands (Parsing).

     Caution: Before sending the string to the system, Gri first translates any synonyms present.  Be careful with this, since system commands calling awk, etc, very often use backslashes for the newline character \n within strings.  If you have a synonym whose name starts with \n, you can get a conflict.  For example, the awk command print "foo\nbar"; should print a line with foo on it, followed by a line with bar on it, but it will instead print a single line with fooMISTAKE, if you had previously defined a synonym as \nbar = "MISTAKE".  One way to avoid this mistake is to make sure any \n characters appear at the end of strings, and then simply avoid having a synonym named \n.

     Here is a Perl example.

          \m = "Foo bar"
          system perl <<"EOF"
          $a = 100;
          print "foo bar is \m, and a is $a\n";
          print "BETTER: foo bar is \m, and a is $a\n";
          print "Q: was a 100?\n";
          EOF

Some more examples:

  * To get the first 15 lines of a file called foo.dat inserted into another file called bar.dat, you might do the following.  Only the first method works; the second will fail because .n. will not be translated before passing to the operating system.

          \num = "-15"
          system head \num foo.dat > bar.dat
          # Following will not work correctly because .num.
          # will not be translated
          .num. = -15
          system head .num. foo.dat > bar.dat

  * Issue a unix command to get a listing of files in the current working directory, and pipe them into the more system command.

          system ls -l *c | more

  * Store the date and time into a synonym, and use it in a title:

          \time = system date
          ...
          draw title "Plotted at time \time"

  * Use awk to prepare a two-column table of x, ranging from 0 to 1 in steps of 0.1, and sin(x).  The table is stored in a file whose suffix is the process ID of the Gri job.  This file is then opened, and the data plotted.  Finally, a system command is issued to remove the temporary file.

          system awk 'BEGIN { \
              for (x=0; x<1; x+=0.1) { \
                printf("%f %f\n", x, sin(x)) \
              } \
            }'  > tmp.\.pid.
          open tmp.\.pid.
          read columns x y
          close
          system rm tmp.\.pid.
          draw curve

     Note: in unix, this command calls the Bourne shell, not the C-shell that is often used interactively.  For many simple uses, the only difference from normal interactive use will be that ~ is not expanded to the home directory.  For example, you should write

          system awk -f $HOME/foo/bar/cmd.gawk

     instead of the

          system awk -f ~/foo/bar/cmd.gawk

     that you might expect from interactive C-shell use.

     RETURN VALUE: Sets \.return_value to system status N status

unlink
------

     `unlink \filename'

Delete a filename and possibly the file to which it refers.  On non-unix machines, this simply means to delete the file.  On unix machines, the action is more subtle.  The unix OS permits several processes to use a given file at once.  Therefore, unlink doesn't immediately remove the file, but instead waits until other processes are done with it.  Most users will never realize the difference, however, and it is safe to think of unlink as simply removing the file.  To learn more, type man unlink in a unix shell.

A common use of unlink is to remove files that were created with the tmpname facility (Using OS Inside Gri), e.g.

     \tmp = tmpname
     # do some system commands to put data into this file
     open \tmp
     read columns x y
     draw curve
     unlink \tmp

while
-----

     `while .test.|{rpn ...}'

Perform statements in loop while the value of .test. or the RPN expression is nonzero.  The end of the loop designated by a line containing the words end while.  The value .test. may be an rpn expression.  To leave the loop prematurely, use a break statement.  Upon encountering a break statement, Gri jumps to the line immediately following the loop.  If the -chatty option is nonzero, a notification is printed every 1000 passes through the loop, as a debugging measure to catch unintended infinite loops.

Examples:

  * Loop forever, printing a message over and over.

          while 1
            show "This loops forever. Need to 'break'"
          end while

  * Read number pairs from a file, plotting bullets at the indicated locations.  Note the use of an infinite loop, with a break condition following an end-of-file test.  (Do not be tempted to write such loops as while !..eof.. because that would not catch the end of file until the next time through the loop.  The result would be to draw the last bullet twice, since the read will not update the variables when the end of file is encountered.)

          while 1
            read .x. .y.
            if ..eof..
              break
            end if
            draw symbol bullet at .x. .y.
          end while

  * Loop 10 times, printing the values of .i. as they range 0, 1, ..., 9.  After exiting from the loop, .i. will equal 10.  Be careful to use the correct rpn greater-than test to avoid an infinite loop.

          .i. = 0
          while {rpn .i. 10 >}
            show .i.
            .i. += 1
          end while

The write commands
------------------

The write commands write various things.

If the filename is stdout, the information is written to the standard output device (ie, the screen); if it is stderr, the information is written to the standard error device (ie, the screen).

IMPORTANT NOTE: The write commands append to the output file, as opposed to overwriting the contents of the file. Therefore if you've run the Gri script before, and want fresh output, make sure to do something like the following

     system rm -f the_grid.dat
     write grid to grid.dat

write columns
.............

     `write columns to \filename'

Append data columns to the end of the indicated file.

write contour
.............

     `write contour .value. to \filename'

Append to the named file the (x,y) pairs defining the contour of the indicated value.

The first line of output is a header line, containing two numbers: the contour value and the missing value.  Then the (x,y) pairs are written a line at a time, with missing values being used to indicate ends of segments.  A blank line is written after the last data pair.  For example, if the contour contained two closed regions, Gri would output a pair of missing values as one of the xy pairs, to denote the separation of the two curves.  You could read and plot the output as in this example

     write contour 10 to contour.out
     open contour.out
     read .contour_value. .missing.
     set missing value .missing.
     read columns x y
     draw curve

write grid
..........

     `write grid to \filename [bycolumns]'

Append grid to the end of the named file.  Storage is in %f format, and is in normal image order.  If the keyword bycolumns is present, then the grid is transposed first, in such a way that read grid data bycolumns performed on that file will read back the original grid data.

write image
...........

     `write image ... to \filename'

The variants of this command write various things about the image to the named file, as illustrated in the following table.

  * write image to image.dat Append image to the end of the named file.  Storage is by unsigned-char, and is in normal image order.  There is no header.

  * write image rasterfile to image.dat Append image to the end of the named file, in Sun Rasterfile format.

  * write image pgm to mask.dat Append image mask to the end of the named file, in PGM 'rawbits' format.

  * write image mask to mask.dat Append image mask to the end of the named file. Storage is by unsigned-char, and is in normal image order.

  * write image mask rasterfile to mask.dat Append image mask to the end of the named file, in Sun Rasterfile format.

  * write image mask pgm to mask.dat Append image mask to the end of the named file, in PGM 'rawbits' format.

  * write image colorscale to colorscale.dat Append image colorscale transform to the end of the named file.  Storage is a series of 256 lines, each containing 3 numbers (for Red, Green and Blue) in the range 0 to 1.  The file is suitable for reading with the read image colorscale command.

  * write image grayscale to grayscale.dat Append image grayscale transform to the end of the named file.  Storage is a series of 256 lines, each containing a number in the range 0 to 1. The file is suitable for reading with the read image grayscale command.

Programming in the Gri Language
*******************************

The Gri programming language has if statements to control program flow, and a while statement to repeat commands.  There are two data types in Gri: ``variables'' (to store numbers) and ``synonyms'' (to store character strings).  Gri recognizes commands by matching statements against its list of known commands.  This list is extensible; it is easy to add new commands as extensions to Gri.

Defaults
========

At startup time, Gri sets the values of some things, like font size. Since Gri is still under development, some of these defaults might change, so you should not rely on them remaining the same.    Presently, the defaults are equivalent to:

     set arrow size 0.2         # (cm)
     set axes style 0
     set beep off
     set clip off
     set clip postscript off
     set contour format %lg
     set contour label position ? ?
     set contour labels horizontal
     set contour labels whiteunder
     set dash off
     set font size 12           # (pt)
     set font to helvetica
     set graylevel 0            # Black ink
     set ignore initial newline off
     set input data window x off
     set input data window y off
     # Following set (curve, axes, symbol) widths to width
     # of rapidograph pens called (6x0, 3x0,  6x0)
     set line width 0.709        # (pt) for curves
     set line width axis 0.369   # (pt) for axes
     set line width symbol 0.369 # (pt) for symbols
     set missing value 1.0e22
     set page portrait
     set page factor 1
     set symbol size 0.1        # (cm)
     set tic size 0.2           # (cm)
     set tics out
     set trace off
     set x format %lg
     set x margin 6.0           # (cm)
     set x name "x"
     set x size 10              # (cm)
     set x type linear
     set y axis name vertical
     set y format %lg
     set y margin 6.0           # (cm)
     set y name "y"
     set y size 10              # (cm)
     set y type linear

(NOTE: Programmers may alter the gri source file defaults.h and then recompile Gri, if they feel the need to change these things.  Also, see the file startup.c and the function gr_begin() in gr.c.)

Online Help
===========

Type help to get a list of available commands and other topics of interest. Here's how Gri responds

     Type `help' followed by a command-name:
      assert      cd            close         convert
      create      debug         delete        differentiate
      draw        expecting     filter        flip
      get         help          if            ignore
      input       insert        interpolate   list
      ls          mask          move          new
      open        pwd           query         quit
      read        regress       reorder       rescale
      resize      return        rewind        set
      show        skip          sleep         smooth
      source      sprintf       state         superuser
      system      write
     Or type `help -' followed by a topic from this list:
      example     extending     files         math
      strings     synonyms      variables     manual

Some commands have more words than shown.  You can type these additional words to narrow the help down; otherwise Gri will give you help on all commands that begin with the indicated words.  For example, try help set and help set x.  When you ask for help on a multi-word command, Gri tells you about all commands which begin with the words you've typed.  Thus,

     help
     help draw
     help draw zero
     help draw zero line

narrow in on the command draw zero line.  The response to the most complete request is

     `draw zero line [horizontally|vertically]'
       draw zero line
         Draw line y=0 if it is within axes
       draw zero line horizontally
         Draw line y=0 if it is within axes
       draw zero line vertically
         Draw line x=0 if it is within axes

The part enclosed in angled quotes is the syntactical description of the command.  (NOTE: The square brackets indicate an optional word (in this case) or words.  The vertical bar indicates that either the item on the left or the item on the right may appear; it is a logical OR operator. The only other special characters in syntax descriptions are the braces {}, which are used to enclose multiple words which act as one unit; they are used to clarify the choices presented to the OR operator.)  Following the syntactical description are examples.  Each example is indented 2 spaces, and a description of it (which always starts with an upper-case character and ends with a period, to indicate that it is an English description) follows that, indented by an additional 2 spaces.

Long Command Lines
==================

To extend a command across several lines, use a backslash \ at the very end of all lines but the last:

     draw line from \
       10 20 \
       to \
       10 30

Variables
=========

About variables
---------------

Variables store numbers.  As it reads your program, Gri substitutes variable values any place a variable appears where a number normally would.  For example, in the code below .number. is a variable storing the value 10, so the two read statements have the same effect:

     .number. = 10
     read columns .number. x y
     read columns 10 x y

Variable names begin and end with a single period (example: .num.).  (Gri uses this odd notation to distinguish variable names from ``normal'' words, which is necessary because Gri does not have a limited list of keywords as other languages do.  Thus, the C programming language is happy to let you use a variable name like latitude, since it is not a keyword, but Gri is not, since it might like to use that word itself in a new command.)

You should not use names beginning and ending with double periods, because Gri uses names like that to store built-in variables for its own use (e.g., ..xsize.. saves the width of the plot).

To store a number into a variable, use a command like

     .time. = 10

or

     .time. = {rpn 10 sin}

Storage is automatically set aside when you assign into a nonexistent variable; no ``declaration'' statements are required as in the C language.

The Gri command, new (New), allows you to have several ``versions'' of a variable.  This is useful for local storage in new commands, inside if statements, etc, since it lets you use temporary variables without worrying about overwriting values outside the local block of code.  The syntax is new .variable. = value (where, as usual, value may be an rpn expression (rpn Mathematics).  Here is an example:

     `foo bar'
     {
       new .a.         # Get storage
       .a. = 10        # Store a local value
       show "Locally, .a.=" .a. " (expect 10)"
       delete .a.      # Delete this local one
     }
     .a. = 1
     show "Global version has .a.=" .a. " (expect 1)"
     foo bar

To see if a given named variable (or synonym) exists, use the RPN operator defined (rpn Mathematics).

User variables
--------------

You can get Gri to read values for variables from your file.  Here's how to read a number from a header line and then read that many lines of columnar data:

     open file.dat
     read .num.
     read columns .num. x y

You can define variables within the Gri program:

     .num. = 10
     read columns .num. x y

You can get variables interactively from the user, using the query command.  (If the user types carriage-return, or if the command-line flag -y was specified when invoking Gri, the value 100 will be assigned to .num.). For example,

     query .num. "Number of rows to read?" (100)
     read columns .num. x y

Gri allows you to use a previous value of the variable in the default string, as in this example:

     .start. = 8                             # default
     .stop. = 2                              # default
     query .start. "Start time? " (.start.)
     query .stop.  "Stop time?  " (.stop.)

Variables can be manipulated using reverse polish notation (RPN) mathematical operations (rpn Mathematics).

Variables are often useful in if statements.  Here are some examples:

     read .num_pts.
     if .num_pts.
       show "There are some data"
       read columns .num_pts. x y
     else
       show "There are no data"
     end if
     # ...
     read .latitude.
     if {rpn .latitude. 10 <}
       read .num.
       read .num. x y
       draw curve
     else
       show "Skipping data North of 10deg N"
       read .num.
       skip .num.
     end if

Built-in variables
------------------

Built-in variables (Index of Builtins) have names which begin and end with two periods.  For example, ..xsize.. is the width of the x-axis in centimetres.  You may use these variables as you wish (example: ..xsize.. = 4 is an alternative to set x size 4), but you must be aware that these are not ``free'' variables for you to use for arbitrary purposes.  You can find out what the built-in variables are by the command show variables.

There are two types of variables

  * Startup variables, which are created by Gri at startup time. These variables can be relied upon to exist (barring changes in Gri itself), unless you delete them.

  * Spontaneous variables (which are created by certain Gri commands, and only exist if these commands have been executed).  For example, the regress command defines ..coeff0.. (the intercept of the fitted line), ..coeff1.. (the slope of the fitted line), ..R2.. (the correlation coefficient).

To see the values of the built-in variables (along with the user variables), use show variables.  Here are some useful builtin variables:

  * ..arrowsize.. Stores either a positive number representing the halfwidth of arrowheads measured in centimetres, or a negative number giving the negative of the ratio of arrowhead halfwidth to arrow length (Set Arrow Size).

  * ..batch.. Flag used for batch mode.

  * ..debug.. Equal to 1 if the -debug command-line flag was set.  Flag used for debugging (Invoking Gri).  The ..debug.. built-in variable is useful in isolating code to use only in test runs. For example, you might use

          if ..debug..
            show "Following are the column data"
            show columns
          end if

     When you run the program with command-line gri -debug file.gri the code in the if block will print out the columnar data, but when you run it with gri file.gri these lines are not printed.

  * ..eof.. Flag indicating whether an end-of-file was encountered on the last read columns.

  * ..words_in_dataline.. Number of words on last dataline.  This is useful in constructs like

          open tmp.dat
          .num. = 0
          while 1
            read .a. .b.
            if !..words_in_dataline..
              show "Got empty line or EOF, so break loop"
              break
            end if
            show "a=" .a. "b=" .b.
            show "; words in line=" ..words_in_dataline..
            .num. += 1
          end while
          show "Got " .num. "data lines."

  * ..fontsize.. Size of letters, measured in points; there are 72.27 points in an inch and 28.45 points in a centimetre.  The mathematical operators pttocm and cmtopt, which do conversion between points and centimetres, are often useful in labelling data curves (rpn Mathematics).

  * ..graylevel.. Graylevel to use in drawing lines, text, etc.  Black ink is 0; white paper is 1.  See also ..red.. etc.

  * ..image_height.. Height of image, or 0 if no image defined yet.

  * ..image_width.. Width of image, or 0 if no image defined yet.

  * ..length_dash.. Length in cm of dashes in dashed lines.

  * ..length_blank.. Length in cm of blanks in dashed lines.

  * ..linewidth.. Width of lines for data curves (Set Line Width).

  * ..linewidthaxis.. Width of lines on axes (Set Line Width).

  * ..linewidthsymbol.. Width of lines in symbols (Set Line Width).

  * ..missingvalue.. Missing value code, also stored in the synonym \.missingvalue.; (Set Missing Value).

  * ..num_col_data.. Number of column data that exist.  You might want to use this after read columns to see if a data file actually had any data in it, or use it in accessing individual elements of columns (rpn Mathematics).

  * ..publication.. Flag for final copy of plot.  The command-line option -p sets the value of ..publication.. to 1.  A typical, and highly recommended, code fragment is

          if !..publication..
            draw time stamp
          end if

  * ..red.., ..green.., ..blue.. Description of present color.  The values are between 0 and 1, with (0,0,0) being black and (1,1,1) being white.  If color is gray, all these will be equal.  You may assign to these, but it will not change the color.

  * ..symbolsize.. Size of symbols in centimetres.

  * ..superuser.. Equal to 0 if the flag was not set, or equal to the flag if it was.

  * ..tic_direction.. Direction of axis tics, 1 for inside or 0 for outside.

  * ..tic_size.. Size of axis tics in centimetres.

  * ..trace.. Equal to 1 if the -trace command-line flag was set.  Used for tracing program execution.

  * ..xinc.. x increment on axes.

  * ..xleft.. x value at left of plot.

  * ..xmargin.. Left margin, in centimetres.

  * ..xright.. x value at right of plot.

  * ..xsize.. x-axis length in centimetres.

  * ..ybottom.. y value at bottom of plot.

  * ..yinc.. y increment on axes.

  * ..ymargin.. Bottom margin in centimetres.

  * ..ysize.. y-axis length in centimetres.

  * ..ytop.. y value at top of plot

  * ..exit_status.. The exit status from the most recent system call (or 0 if no system calls have been done yet).

You may use any of these built-in variables anywhere.  For example, here's how to stack 3 graphs vertically on the page:

     .offset. = {rpn ..ysize.. 3 + }
     open file1
     read columns x y
     close
     draw axes
     draw curve

     ..ymargin.. += .offset.
     open file2
     read columns x y
     draw axes
     draw curve
     close

     ..ymargin.. += .offset.
     open file3
     read columns x y
     draw axes
     draw curve
     close

The first line needs a bit of explanation. It is a reverse-polish expression.  The format is { followed by rpn followed by an expression followed by }.  Within the expression, spaces must separate operands.  This makes .offset. equal to the height of y-axis plus 3 cm, so plots are separated by 3 cm.  To learn more about {rpn ... } (rpn Mathematics).

Another possibly unfamiliar thing is the code +=.  It means take the thing on the left hand side, and add to it the thing on the right hand side.  (In this case, it is used to increase the y margin by the value of .offset..)

Synonyms
========

Synonyms are used by Gri to store character strings.  Gri denotes synonyms with words beginning with backslash (e.g., \syn), following the TeX convention.

Naming convention for synonyms
------------------------------

Synonym names begin with a backslash (e.g., \filename).  After the backslash, Gri expects a letter (upper or lower case) or one or more periods.  Following this is an arbitrary string of letters, numbers, or underscores.  If there are periods at the start, then the same number of periods must be used at the end.  The following are some examples

     \simple = "Howdie"
     \.longer_example. = "Dots and underscores are ok too"
     \a2 = "OK for number at end ..."
     \a3bb = "... and inside"

Gri defines several synonyms for its own use, so that if you modify these, you may get strange results.  Each of these starts and ends with a single period.

There is an exception to the above rule, one which mostly comes up when using netCDF files which may have variable names that may contain punctuation.  Gri permits synonym names to have punctuation characters (but not blanks or tabs) in synonym names, provided that the second character in the name is an opening brace and that the last character is a closing brace, e.g.

     \{foo.bar} = "Foo bar"

This is used particularly for files in the netCDF format, for reading variable attributes, which by netCDF convention use a colon (:) to separate variable name and attribute name (Read Synonym or Variable).  For more information on netCDF format, see

http://www.unidata.ucar.edu/packages/netcdf/index.html

Synonyms may be freely embedded in strings (a common example is draw title "Data from file `\datafile'".  They may also appear anywhere in commands (e.g., open \filename).  The exception to this rule is that Gri ignores your synonyms within math mode, in order to prevent clashes (e.g. you might define \alpha as a synonym storing the value "foo bar", but Gri will ignore this within math-mode, so that $\alpha$ will still mean the Greek letter alpha).

To get a backslash in a string without Gri thinking it is part of a synonym, use two backslashes (e.g., show "The backslash character \\ is used for synonyms.").  This may sometimes be required in system commands (System), to prevent Gri from converting substrings like \n (which many system commands use to represent the newline character).  For example, the command system perl -e 'print "foo\nbar";' will be mangled if Gri has already been told that \nbar is a synonym.  (There will be no problem if \nbar is not an existing synonym, since Gri will then just leave it in place.) To be sure that no mangling can occur, replace each backslash with two backslashes.  This tells Gri not to try to substitute a synonym at that location.  In the example below, the first system call prints fooled you! on one line line, because Gri substituted for what it thought was a synonym called \nbar; the second (correctly) prints foo on one line and bar on the next.

     \nbar = "led you!"
     system perl -e 'print "foo\nbar\n";'
     system perl -e 'print "foo\\nbar\\n";'

Similarly, if your system command is expecting to see \t (for a tab character), then you must write \\t to prevent Gri from trying to substitute a synonym named \t.

The show command has a special syntax for permitting newlines and tabs in strings (Show).

Some uses for synonyms
----------------------

Synonyms store strings and are useful for anything strings are useful for, e.g. filenames, plot labels, names of variables, etc.

Using synonyms to generalize code
.................................

Synonyms are often used to store filenames, since then only a single line of a file may need to be altered, in order to work with another file, e.g.

     \filename = "columns.dat"
     open \filename
     # a lot more code using the file name

Using synonyms to store OS output
.................................

Synonyms provided a convenient way to store information from the OS.

     # Show the date.
     \date = system date
     show "Time is \date"

     # Show the command file name, then use the system
     # to construct a filename with the same beginning
     # but ".dat" as the ending instead of ".gri".
     show "The commandfile name is \.command_file."
     \fn = system echo `basename \.command_file. .gri`.dat
     show "A filename constructed from this is \fn"

This example uses the Unix system commands echo and basename to  construct a filename ending in .dat, from the command file name (stored in the builtin string \.command_file.), assuming that the command file name ends in .gri.

NOTE: As usual, if the system command contains the Gri comment designator (the string #), protect it with double-quotes (System).

Storing user responses via query
................................

You can ask the user for the contents of strings:

     query \filename "What's the data file?" ("file.dat")

The prompt What's the name of the data file? is typed to the terminal, and whatever string the user types is inserted into the synonym \filename. If the user types nothing, but simply presses carriage return, the (optional) default string (which must be enclosed in parentheses as shown) is put into \filename. Note that the default is ignored if it is not written properly: it must be enclosed in double quotes enclosed in parentheses, with no intervening spaces.

Storing File Contents
.....................

You can read the contents of synonyms from a file:

     open \directory_file
     read \file_name
     close
     open \file_name
     read columns x y

The first (space-separated) word is read into the the first synonym after the read command, the second word into the second synonym, and so on. If the word you want is not near the front of the line, you can use the command read line to get the whole line, then use the method described above to extract the word you want.  Indexing begins with 0, remember.

Working with words within strings
.................................

Sometimes a synonym will contain several words that you need to work with indidually (e.g. it might contain a list of files that should be processed).  There are two ways to do this.

The word of syntax.

          \sentence = "This sentence has five words"
          \first_word = word 0 of "\sentence"
          \last_word = word 4 of "This sentence has five words"

The [] syntax
     Individual words of synonyms may be accessed by prefixing the synonym name with the index number of the word (starting at 0) enclosed in square brackets.

     The number in the square brackets may be a constant, a variable, or a synonym, but not a more complicated expression.  If the index value is a floating-point number, it is first rounded to the nearest integer.  If the index value is negative or exceeds the number of words minus 1, then an empty string is retrieved.

     If no number appears in the square brackets, the result is the number of words in a synonym.

          \syn = "This has 4 words in it"
          show "\[0]syn   ... gives 'This'"
          show "\[1]syn   ... gives 'has'"
          .i. = 3
          show \[.i.]syn  ... gives 'words'"
          \i = "3"
          show \[\i]syn   ... gives 'words'"
          show "\[]syn    ... gives '6', i.e. number of words"

Some important builtin synonyms
-------------------------------

Within mathematics mode (portions of strings enclosed within dollar-signs), Gri stores the definitions of many Greek letters and mathematical symbols as math-mode synonyms (Mathematical Text).

Global synonyms are shared among commands.  To see the built-in global synonyms (Index of Builtins) use show synonyms, which produces output that looks something like the following.

     Synonyms...
         \.missingvalue.           = "10000000000000000000000.000000"
         \.return_value.           = ""
         \.version.                = "2.7.0"
         \.pid.                    = "3043"
         \.wd.                     = "/home/kelley"
         \.time.                   = "Sun May 20 13:18:32 2001"
         \.user.                   = "kelley"
         \.host.                   = "Intrusion.phys.ocean.dal.ca"
         \.system.                 = "unix"
         \.home.                   = "/home/kelley"
         \.lib_dir.                = "/usr/share/gri"
         \.command_file.           = "stdin"
         \.readfrom_file.          = "stdin"
         \.ps_file.                = "gri-00.ps"
         \.path_data.              = "."
         \.path_commands.          = "."

These things will be obvious to unix users; for example \.pid. is the process ID of the job (often used in names for temporary files), and \.wd. is the working directory (often used in draw title commands to indicate in which directory the gri job was run.

Some commands set \.return_value. to non-blank; the meaning of the return value varies from command to command.

Alias synonyms: the \@alias syntax
----------------------------------

Sometimes you need to work with a variable or a synonym whose name can only be determined at run-time, perhaps through interaction with the user, examination of a datafile, or examination of the command provided to the OS when invoking Gri.

Gri handles this by so-called "alias" synonyms, which store the names of other items.

The syntax is simple.  Suppose that a synonym, called \pointer say, contains the name of another synonym, or a variable.  Then you may use \@pointer anyplace you would normally use the item named.

Illustrations of using the value of a named item
     The following prints an approximation to Pi followed by the name of movie star.

          .pi. = 3.14
          \pi_pointer = ".pi."
          show \@pi_pointer  # just like 'show .pi.'

          \hero = "Gregory Peck"
          \our_hero = "\\hero"
          show "\@our_hero"  # just like 'show "\hero"'

Illustrations of assigning to a named item
     The following prints an approximation to 2*Pi and yet another star; the point is that the alias appears to the left of an assignment operator.

          # Print approximation to 2*Pi
          .pi. = 3.14
          \pi_pointer = ".pi."
          \@pi_pointer *= 2
          show .pi.

          # Stars don't shine alone
          \hero = "Gregory Peck"
          \our_hero = "\\hero"
          \@our_hero = "Harrison Ford"
          show "\hero"

Local synonyms
--------------

Local synonyms are created by Gri upon entry to a Gri command.  You use them to parse the command line that was used in calling the new command, to look for options, gather filenames, etc.  Local synonyms are known only from within the local Gri command.  They are not listed by show synonyms, but they can be used freely in commands like show "Number of words is \.words.".

  * Within any new Gri command, the number of words in the line that called the command is available in \.words..  The RPN operator wordc also yields the same value (Solitary Operators).

  * The first word in the calling line is \.word0., the second \.word1., etc.  (Note that this is the C convention, not the FORTRAN convention.  If \.words. is 2, then \.word0. and \.word1. are defined, but \.word2., which FORTRAN programmers expect, will not be defined.)  If you don't know the place of the synonym in advance (i.e. 0 versus 1, for \.word0. versus \.word1.), then use the RPN operator wordv instead (Unary Operators).

  * Within any new Gri command, the proper calling usage is available in \.proper_usage..  This is useful in tests of syntax (Adding New Commands).  For example:

          `draw depths from \file'
          Draw depth data stored in indicated file.  If the
          filename contains periods or slashes, you'll
          have to enclose it in double quotes, as
          in the second example:
            draw depths from file upper_cove
            draw depths from file ../old_data/upper_cove
          {
            if {rpn \.words. 4 !=}
              show "FATAL ERROR in `\.proper_usage.':"
              show "  Need 4 words; got \.words. words."
              quit
            end if
            # Right number of words, so continue onward...
          }

These synonyms help you scan for optional words in commands.  Suppose you have defined a new command New Thing [option].  If you call it with New Thing, then (within New Thing) \.words. will be "2", \.word0. will be "New" and \.word1. will be "Thing".  On the other hand, if you call it with New Thing 22.3 then \.words. will be 3, \.word0. will be "New", \.word1. will be "Thing" as before, and \.word2. will be "22.3".

EXAMPLE  Here is a new command to label lines drawn by draw curve:

     `Draw Label For Last Curve "label"'
     Draw a label for the last curve drawn, using
     ..xlast.. and ..ylast.. built-in variables.
     {
       new .draw_label_for_last_curve_graylevel.
       .draw_label_for_last_curve_graylevel. = ..graylevel..
       set graylevel 0
       draw label "\.word5." at \
           {rpn ..xlast.. xusertocm 0.1 + xcmtouser} \
           {rpn ..ylast.. yusertocm \
               ..fontsize.. pttocm 2 / -
               ycmtouser}
       set graylevel .draw_label_for_last_curve_graylevel.
       delete .draw_label_for_last_curve_graylevel.
     }
     open file.dat
     read columns x y
     draw curve
     \label = "Illustration"
     Draw Label For Last Curve "\label"

(Note that Gri has a built-in command draw label for last curve "\label" written much as above, so there is no need for you to enter this new command into your .grirc file.  But you might want to check gri.cmd to see how a full command does checking of the calling syntax (Invoking Gri).

If Statements
=============

Gri has if statements to make your programs more flexible. Here's an example:

     query \thick "Use thick lines? (0 or 1)" ("0")
     if \thick
       set line width 2
     else
       set line width 0.5
     end if

If you answer 1 to the question, the line thickness will be set at 2 points.  If you answer 0 then a thin line will be used.  If you press carriage return a thin line will be used.

The item following the if can be

  * a number (1 means true; anything else means false)

  * a variable (1 means true; anything else means false). Example:

          if .plot_contours.
            draw contour
          end if

  * a synonym which expands to a number (1 means true; anything else means false). Example:

          \plot_contours = "1"
          if \plot_contours
            draw contour
          end if

     (Don't worry about the fact that synonyms are strings; Gri expands the string value before interpreting the if statement.)

  * an expression of the form {string1 == string2 }.  The symbol == is an operator which tests for string equality.  This expands to 1 if the strings are equal, or 0 otherwise.  The strings may be either synonyms or string constants.  If the string constant contains only one word, then it is not necessary to enclose it in quotes, but it is clearer to do so.  Examples:

          if {"\variable" == "Salinity"}
            set x name "Salinity"
          else
            set x name "Unknown"
          end if

  * a rpn (reverse polish notation) expression (rpn Mathematics):

          if {rpn .time. 100 <}
            # ie, (100 < time), not (time < 100)
            show "Time > 100"
          else if {rpn .time. 100 >}
            show "Time < 100"
          else if {rpn "\item" "later" ==}
            show "Time ... later babe"
          else
            show "Time is equal to 100"
          end if
          if {rpn .time. 10 * 100 ==}
            show "Time is equal to 10"
          else
            show "Time is not equal to 10"
          end if

There is no need to put the else part in if you don't need it. You can do

     set line width 0.5
     if \use_thick_lines
       set line width 2
     end if

if you wish.

If you want just the else part, you can do

     if ! \use_thick_lines
       set line width 0.5
     end if

(The exclamation point denotes logical negation: ! true equals false.)

If statements may be nested many levels deep.  You may also have else if blocks, as in:

     if {"\variable" == "S"}
       set x name "Salinity"
       set x axis 32 33 0.5 .1
     else if {"\variable" == "T"}
       set x name "Temperature"
       set x axis 15 20 1 0.5
     else
       set x name "Unknown"
     end if

Loops
=====

Gri provides only one type of loop, the while loop, described elsewhere (While).

Mathematics
===========

Gri lets you do some simple mathematical manipulations on your column and grid data.

Column data
-----------

The column operators are =, +=, -=, *=, /=, ^= (exponentiation) and _= (logarithm).  There must be spaces before and after the operators, but no space between the 2 letters of the operators. The operations may be applied not only to x and y as shown, but also to z (used to hold data to be contoured or written as symbols), and u and v (used to store vector fields).

The axis scales are not changed by mathematical operations on the columns, regardless of whether the scales were set manually or by Gri command (Axis Scaling).

Elements of columns are available by the @ reverse polish operator (rpn Mathematics).

Examples:

  * To multiply all the x data by 10, use x *= 10; to add 5 to each y-value, use y += 5.

  * To set all the y data to 10, do y = 10.  (This will only work if you've already read column data.)

See also Tertiary Operators for a method of assigning or altering column data using the RPN operator.

Grid data
---------

Various commands let you alter grid data as used in contouring (Contour Plots).  Possible commands are as follows.

     grid data = number
     grid data += number
     grid data -= number
     grid data *= number
     grid data /= number
     grid data ^= number # take data to power 'number'
     grid data _= number # take log base 'number'
     grid x = number
     grid x += number
     #... others as in `grid data'
     grid y = number
     grid y += number
     #... others as in `grid data'

Image data
..........

Various commands let you alter image data (Images.). Possible commands are as follows.

     image += number
     image -= number
     image *= number
     image /= number
     image ^= number # power
     image _= number # logarithm

Image grayscale/colorscale
..........................

Various commands let you alter image data (Images). Possible commands are as follows.

     image grayscale += number
     image grayscale  -= number
     image grayscale  *= number
     image grayscale  /= number
     image grayscale  ^= number # power
     image grayscale  _= number # logarithm
     image colorscale += number
     image colorscale  -= number
     image colorscale  *= number
     image colorscale  /= number
     image colorscale  ^= number # power
     image colorscale  _= number # logarithm

Variables
.........

Possible commands are:

     .variable. = number
     .variable. += number
     .variable. -= number
     .variable. *= number
     .variable. /= number
     .variable. ^= number # power
     .variable. _= number # logarithm

Rpn (reverse-polish notation) Calculator
========================================

Gri can do simple mathematics on numbers.  The syntax is reverse-polish notation (rpn), which is used in some calculators.  Most users can learn rpn in a few minutes, so don't worry if you don't know RPN yet.

Syntax: rpn expressions can be used anywhere Gri expects a number. RPN expressions start with a opening curly brace ({) which is immediately followed by the word rpn.  rpn expressions end with a closing curly brace (}).  Instead of set x size 10 you could write set x size {rpn 20 2 /}, where the expression {rpn 20 2 /} tells Gri to insert the number 20 onto a stack, then insert the number 2 above it on the stack, and then divide the top two items on the stack.  The following are equivalent:

     set x size {rpn 20 2 /}           # 10 = 20/2
     set x size {rpn 30 2 / 5 -}       # 10 = (30/2-5)
     set x size {rpn pi 3.1415 / 10 *} # 10 = 10*pi/pi

If an rpn expression contains a variable whose value is ``missing'', then the value of the result of the expression will also be missing (unless the value of the missing variable is thrown away with a ``pop'' operator).  However, if a missing value just happens to occur as the result of an intermediate calculation, then the result is not considered to be missing.

RPN operations can be divided roughly into the following groups.

Stack Operators
---------------

Stack operators manipulate or display the stack.

pop removes the top item from the stack (Unary Operators).

dup duplicates the top item on the stack (Unary Operators).

exch reorders the top two items on the stack (Binary Operators).

pstack prints the items on the stack (without changing the stack).

roll_right rolls the items to the right.

roll_left rolls the items to the left.

For example, the following shows how you might use exch or roll_right to change the sense of a subtraction.

     show {rpn 1 2            -} " ... yields -1"
     show {rpn 1 2 exch       -} " ... yields  1"
     show {rpn 1 2 roll_right -} " ... yields  1"

Rpn function Operators
----------------------

rpnfunction operators are user-defined operators.  The parser replaces any such operator with the user-defined rpn expression.  The rpnfunction operators are both general and powerful.  An rpnfunction may be composed of any legal primitive rpn constructs or even other legal rpnfunction constructs.  For details, (Rpnfunction).

Tertiary Rpn Operators
----------------------

{rpn 0 4 "hello" substr }
     Extract 4 characters from the indicated string, starting at character number 0 (i.e. the start of the string).  In other words, replace the three items on the top of the stack with the single item \"hell\".

Binary Operators
----------------

Binary operators act on the top two items on the stack.  Most binary operators replace two items on the stack with one item, e.g. {rpn 1 2 /} yields 0.5.  However, a few binary operators replace one pair of items with a new pair of items, e.g. the xyusertocm operator replaces an (x,y) pair in user coordinates with an (xcm,ycm) pair in coordinates of centimeters on the page.

The binary operators are illustrated below, in rough alphabetical order.

{rpn 3 2 +}
     Add 2 to 3.

{rpn 3 2 -}
     Subtract 2 from 3.

{rpn 3 2 *}
     Multiply 3 by 2.

{rpn 3 2 /}
     Divide 3 by 2.

{rpn 3 2 <}

     Test whether 2 is less than 3, yielding 1.  Note: this convention may be confusing to users who are familiar with HP calculators from decades past.  Present-day calculators use this convention, but possibly older calculators used the reverse convention, using > where Gri uses <.

{rpn 3 2 <=}
     Test whether 2 is less than or equal to 3.

{rpn 3 2 >}
     Test whether 2 is greater than 3, yielding 0.

{rpn 3 2 >=}
     Test whether 2 is greater than or equal to 3, yielding 0.

{rpn 3 2 ==}
     Test whether 2 and 3 are equal, yielding 0.  (Do not confuse this with the asignment operator =, described next.)

{rpn 10 ".ten." =}

     Assign the value 10 to the variable named .ten..  The variable name must be put in quotes, or else Gri will insert the value of the variable (if it exists) into the expression, instead of trying to assign to it.

     After the assignment is done, the stack is cleared of both the value and the variable name.  For example, in the following code

          {rpn 3.1415 ".pi." =}
          show .pi.

     the first line evaluates to a blank line, and the second prints the value of Pi.

     NOTE: Do not confuse this with the == equality operator described above.

{rpn "hello" "\\greeting" =}
     Assign the value "hello" to the synonym \greeting.  See notes at the above item.

{rpn 3.14159 0 "x" =}
     Assign the value Pi to the first element (at index 0) of the x column.  All columns may be assigned to in this way, e.g. the following is a technique for plotting a quadratic function:

          .i. = 0
          .n. = 10
          while {rpn .i. .n. >}
              {rpn .i. .n. 1 - /     .i. "x" =}
              {rpn x .i. @ 2 power  .i. "y" =}
              .i. += 1
          end while
          draw curve

{rpn 0 1 &}
     Test whether 0 and 1 are both true, yielding 0.

{rpn 0 1 and}
     Test whether 0 and 1 are both true, yielding 0.

{rpn y x area}
     Calculate the area under the curve y=y(x).  For details (Manipulation of Columns etc).

{rpn 0 1 |}
     Test whether either 0 or 1 is true, yielding 1.

{rpn 0 1 or}
     Test whether either 0 or 1 is true, yielding 1.

{rpn 2 3 exch}
     Exchange 2 and 3 on the stack, yielding 3 2 on the stack.  (See also pop and dup.)

{rpn x 0 @}
     Yields the value of the first number in the x column.  A similar form also works for y, etc.  (Manipulation of Columns etc).

{rpn 2 3 inf}
     Pick the smaller of two values, yielding 3.  (Opposite to sup.)

{rpn 2 3 power}
     Take 2 to the 3rd power, yielding 8.  Note: This convention may be confusing to users who are familiar with HP calculators from decades past.  Present-day calculators use this convention, which they write as y^x, but older calculators used the reverse convention, labelling the key x^y.

{rpn 2 3 remainder}
     Calculate the remainder after dividing 2 by 3, yielding 2.  The return value for {rpn A B remainder} is B - n * A, where n is the quotient of A/B, rounded towards zero to an integer.  In this case, 2/3 rounds to an n value of zero, yielding 2 as the resulting remainder.

{rpn "heLLo" "s/L/l/g" sed}
     Switch all instances of L into l, yielding the string "hello" on the stack.  This can be helpful for working with filenames, etc.  The work is preformed with a system call to the sed utility (present on unix systems), and therefore this command will fail if sed is not installed, or if the OS cannot be contacted.

{rpn "file" ".dat" strcat}
     Concatenate the two strings, yielding the string "file.dat".

{rpn 2 3 sup}
     Pick the larger of two values, yielding 3.  (Opposite to inf.)

Unary Operators
---------------

Unary operators replace the last item on the stack with another item. For example, the sin operator takes the sine of the number on the top of the stack; e.g., {rpn 45 sin} yields the sine of 45 degrees.

The unary operators are illustrated below, in rough alphabetical order.

{rpn 0 !}
     Replace 0 (false) with its logical negation 1 (true).

{rpn 0 not}
     Replace 0 (false) with its logical negation 1 (true).

{rpn -3 abs}
     Calculate the absolute value of -3.

{rpn 0.5 acos}
     Calculate the inverse cosine of 0.5, yielding 60 (degrees).

{rpn 2 acosh}
     Calculate the inverse hyperbolic cosine of 2, yielding 1.317.  (Note: argument must equal or exceed 1, or an error results.)

{rpn "filename" age}
     Calculate the ``age'' of the indicated file, in seconds.  An age of zero indicates that the file was created, or last modified, within 1 second of the execution of the age operator.

     On unix (and similar) machines, the calculation is done on unix machines with the stat() subroutine.  On other machines, the age operator may cause an error.

     The age of a non-existent file is reported as the number of seconds since the system clock's reference time, i.e. since 1970-jan-1 on unix machines.  This convention is so that scripts like that in the example below will work as intended.

     A typical use of this command is the creation of data-files from shell scripts, as illustrated below.  The idea is to update (or create) the file file.dat using the system-executable script creator.pl, but only to do so if creator.pl is younger than file.dat.

          if {rpn "file.dat" age "creator.pl" age <}
             system "./creator.pl > file.dat"
          end if
          open file.dat

     For the convenience in such usage, a non-existent file is assigned the maximum possible file age on the given OS, e.g. on a unix machine, the age is reported as though the non-existent file had been created on January 1, 1970 on a unix machine.

{rpn 0.5 asin}
     Calculate the inverse sine of 0.5, yielding 30 (degrees).

{rpn 1 atan}
     Calculate the inverse tangent of 1, yielding 45 (degrees).

{rpn 0.5 atanh}
     Calculate the inverse hyperbolic tangent of 0.5, yielding 0.549306 (radians).

{rpn 0 argv}
     Returns the name of the Gri command-file, which is considered as the first "optional" argument.  (It may seem odd that the name of the command-file is considered an option, but Gri does this for consistency with C and other languages.  It is useful.)  Other arguments provided when Gri was invoked are provided as rpn 1 argv, etc.

     A string consisting of a single blank character results if one tries to access beyond the list of arguments that were actually supplied.  See also the argc solitary operator (Solitary Operators), which returns the number of optional arguments.

     For example, if Gri is invoked as

          gri myscript.gri file1.dat file2.dat

     and if myscript.gri contained

          .n. = {rpn argc}
          .i. = 0
          while {rpn .n. .i. <}
              show "argument " .i. " is " {rpn .i. argv}
              .i. += 1
          end while

     then the output would be

          argument 0 is myscript.gri
          argument 1 is file1.dat
          argument 2 is file2.dat

     For usage within the Emacs gri-mode, see Filename arguments when running gri.

{rpn "hi" ascent}
     Determine ascent of this string (in cm), in the present font and fontsize.  (See also descent and width.)

{rpn "3.1" atof}
     Calculate the numerical value contained in indicated string.

{rpn 1.5 ceil}
     Calculate the next higher integer, yielding 2.  (Opposite of floor.)

{rpn 45 cos}
     Calculate the cosine of 45 degrees, yielding 0.707.

{rpn 1 cosh}
     Calculate the hyperbolic cosine of 1 (radian), yielding 1.543.

{rpn 1 cmtopt}
     Convert from 1 centimeter to so-called ``point'' units, yielding 28.45. (Opposite of pttocm.)

{rpn 170 dec2hex}
     Convert a number into a string which is its hexadecimal representation.  Before the conversion, the number is rounded to the nearest integer, and if the result is negative, an error results.  The string is double-quoted, with letters (if there are any) being in upper case.

     For example \hex = {rpn  63  dec2hex} is equivalent to \hex = "3F".

     Compare with hex2dec, the inverse.

{rpn "\\syn" defined}
     Test whether the synonym is defined at the moment, returning 1 if so and 0 if not.  (Note the double-backslash in the synonym name, which is required.)

{rpn ".var." defined}
     Test whether the variable is defined at the moment, returning 1 if so and 0 if not.

{rpn "\\@alias" defined}
     Test whether the variable/synonym item that is named by the alias (Alias Synonyms) is defined at the moment, returning 1 if so and 0 if not.

{rpn "hi" descent}
     Calculate the descent (below the baseline in cm) for the given string, in the present font and fontsize.  (See also ascent and width.)

{rpn "/home/me/data/timeseries" directory_exists}
     Determine whether indicate directory exists, yielding 1 if it does and 0 otherwise.  (See also file_exists.)

{rpn 2 dup}
     Duplicate the top item on stack, yielding 2 2 on the stack. (See also exch and pop.)

{rpn 1 exp}
     Calculate the value of e raised to the indicated power, yielding 2.71828.

{rpn 2 exp10}
     Calculate the value of 10 raised to the indicated power, yielding 100.

{rpn "foo.dat" file_exists}
     Determine whether the indicate file exists, yielding 1 if it does and 0 otherwise.  (See also directory_exists.)

{rpn 1.5 floor}
     Calculate the nearest smaller integer, yielding 1.  (Opposite of ceil.)

{rpn "AA" hex2dec}
     Convert a string, representing a hexadecimal value, into an integer. The string must be double-quoted, and it may contain either lower- or upper-case letters; this is in contrast to the inverse function, dec2hex, which returns upper-case.

     This operator is most often used in working with colours, since Gri handles colour components in decimal terms, whereas many other applications refer to the components in hexadecimal notation.

     Compare with dec2hex, the inverse.

{rpn 3 ismissing}
     Yields 1 if the indicated value is a ``missing value'' or 0 otherwise.

{rpn 100 log}
     Calculate the base-10 logarithm of 100, yielding 2.

{rpn 10 ln}
     Calculate the natural logarithm of 10, yielding 2.30259.

{rpn x mean}
     Yields the mean value of the (non-missing) numbers in the x column.  A similar form also works for y, etc. (Manipulation of Columns etc).

{rpn x max}
     Yields the largest value of the (non-missing) numbers in the x column.  A similar form also works for y, etc. (Manipulation of Columns etc).

{rpn x min}
     Yields the smallest value of the (non-missing) numbers in the x column.  A similar form also works for y, etc. (Manipulation of Columns etc).

{rpn 28.45 pttocm}
     Calculate the number of centimeters in 28.45 printers points, yielding 1. (Opposite of cmtopt.)

{rpn 1 2 pop}
     Remove the top item from the stack, yielding 1 on the stack. Generates an error if the stack is empty.  (See also exch and dup.)

{rpn 4 sqrt}
     Calculate the square root of 4, yielding 2.  (Negative arguments yield errors.)

{rpn 45 sin}
     Calculate the sine of 45 (degrees), yielding 0.707107.

{rpn 2 sinh}
     Calculate the hyperbolic sine of 2, yielding 3.62686.

{rpn "hello" strlen}
     Determine the number of characters in string, including the quotation marks, e.g. 7 here.

{rpn "date" system}
     Call the indicated system function and insert its ouput on the stack, yielding the date as a character string.

{rpn 45 tan}
     Calculate the tangent of 45 (degrees), yielding 1.

{rpn tanh}
     Calculate the hyperbolic tangent of 2, yielding 0.964028.

{rpn "hi" width}
     Determine width of this string (in cm), in the present font and fontsize. (See also ascent and descent.)

{rpn 0 wordv}
     Returns the first word used in invoking the present command.  Similar to the \.word0. synonym (Local Synonyms).  Example:

          `let us test .it.'
          {
            .w. = 0
            while {rpn .w. wordc >}
              show "The " .w. "-th word is `" {rpn .w. wordv} "'."
              .w. += 1
            end while
          }
          let us test "this thing"
          let us test "this" "thing"
          let us test "Pi is" {rpn 3.14}

     If you are using this to parse options given to the command, it is up to you to skip the non-optional words in the command.  In this case, for example, we skipped the first three words (let, us, and test).

{rpn 1 xusertocm}
     Calculate the x coordinate, in centimeters measured from left-hand side of page, corresponding to a user-value of x=1.  (Opposite of xcmtouser.)

{rpn 1 xcmtouser}
     Calculate the x value, in user units, for a point that is 1 centimeter from the left-hand edge of the paper.  (Opposite of xusertocm.)

{rpn 1 yusertocm}
     Calculate the y coordinate, in centimeters measured from bottom side of page, corresponding to a user-value of x=1.  (Opposite of ycmtouser.)

{rpn 1 ycmtouser}
     Calculate the y value, in user units, for a point that is 1 centimeter from the bottom edge of the paper.  (Opposite of yusertocm.)

Solitary Operators
------------------

Solitary operators do not act on items on the stack; rather, they generate items themselves and insert them on the stack.

The solitary operators are illustrated below, in alphabetical order.

{rpn argc}
     Yields number of command-line arguments given by the user when Gri was invoked.  Thus, invoking Gri as

          gri myfile.gri file1.dat file2.dat

     yields 3, for arguments myfile.gri, file1.dat, and file2.dat.  These arguments are accessible through the argv unary operator (Unary Operators).

{rpn e}
     Yields the base of natural logarithms, i.e. 2.718...

{rpn pi}
     Yields Pi, i.e. 3.141...

{rpn rand}
     Generate a random number in the range 0 to 1, using the C subroutine drand48() if it is available, otherwise the less well-distributed rand() subroutine.

{rpn wordc}
     Returns number of words used in invoking the present command.  Similar to the \.words. synonym (Local Synonyms).  Example:

          `let us test .it.'
          {
            show "This command has " {rpn wordc} " words"
          }
          let us test 10
          let us test {rpn 3 1 +}
          let us test "this"
          let us test "this thing"

     The operator wordv may be used to extract the words of the command (Unary Operators).

Manipulation of Columns etc
---------------------------

Columns
.......

Individual data in the x, y, z, u, v and weight columns can be accessed with the @ operator. The first point has index 0.  Examples:

     show "first x is " {rpn x 0 @ }
     show "last  x is " {rpn x ..num_col_data.. 1 - @ }
     show "and here are all the data:"
     .i. = 0
     while {rpn .i. ..num_col_data.. >}
         show {rpn x .i. @ }
         .i. += 1
     end while

The mean value is available from the mean operator (e.g., .xmean. = {rpn x mean }, while the standard deviation is given by stddev, the skewness is given by skewness, and the kurtosis is given by kurtosis (using the definition that yields 3 for a gaussian distribution).

The minimal and maximal values are given by min and max.

The area under the curve y=y(x) is found by {rpn y x area }, defined by 0.5 * sum ( (y[i] + y[i-1]) * (x[i] - x[i-1]) ) for i ranging from 1 to ..num_col_data..-1.

Grid
....

Grid data can be accessed with e.g. {rpn grid min } , {rpn grid max } , and {rpn grid mean } .

The value of the grid at a given (.x.,.y.) coordinate may be found by by e.g. {rpn grid .x. .y. interpolate}.  The interpolation scheme is the same as that used in converting grids to images.

rpn Examples
------------

Here are some reverse-polish expressions and the corresponding algebraic interpretations:

  * {rpn 1 2 + 10 / } = (1+2)/10

  * {rpn .a. .b. + .c. + .d. / } = (.a.+.b.+.c.)/.d.

  * {rpn e 2 / } = e/2 (Gri knows values of ``e'' and ``pi'')

  * {rpn 23 sin 100 * 12 cos + } = cos(12) + 100sin(23)

  * {rpn 5 2 power } = 25

  * {rpn 2 log exp } = exp(log 2)

  * {rpn 2 ln exp10 } = 10^ln2

  * {rpn 1.7 floor } = 1 (rounds down to nearest integer.  Note that the floor of -1.7 is -2)

  * {rpn 10.1 2 remainder } = 0.1 (remainder of 10.1 after division by 2; see C function remainder(x,y))

  * {rpn -10.1 2 remainder } = -0.1

  * {rpn -10.1 -2 remainder } = -0.1

  * {rpn .num. 10 > } = 1 if 10 exceeds .num., or 0 otherwise

NOTES:

  * The units of sin, cos, etc, are degrees, not radians.

  * The scales of the plot are accessible to rpn.  For example, with the command

          draw label "hi" at 10 20

     you draw the indicated string at the indicated location in user coordinates.  To put it 0.15 centimetres to the right of this location and 0.1 centimetres lower, you could do as follows:

          draw label "\label" at \
              {rpn .x. xusertocm 0.15 + xcmtouser} \
              {rpn .y. yusertocm 0.10 - ycmtouser}

     (Note that the x and y scales have individual translations from "user" to "cm" coordinates.)

  * Some conversion factors are built into rpn; cmtopt converts from centimetres to points (by dividing by 28.45; the conversion factor to inches is 72.27) while pttocm converts from points to centimetres.  For example, here is how to label a data curve with a label placed near the last y-value of the data set:

          draw curve
          .y. = {rpn ..ylast.. yusertocm 0.5 - ycmtouser}
          draw label "Smoothed" at ..xlast.. .y.

Text Strings
============

Any text can be drawn in any size; Gri does not limit font size to a list, e.g. 10 point, 12 points, etc.  Several fonts are available in Gri, e.g. Times, Helvetica, etc.; these are all standard PostScript fonts.  Support for some non-English languages (e.g. French) is also provided.  And, finally, Gri supports inclusion of simple mathematical expressions (Greek letters, superscripts, etc.) in text, using a LaTeX-style syntax.

Embedding synonyms in quoted text strings
-----------------------------------------

Outside math strings, you can embed your synonyms at will.  For example, you can include the name of a data file in the title of your plot as follows

     query \filename "File to read from?" ("data.file")
     open \filename
     read columns x y
     draw curve
     draw title "data from \filename"

Within math strings (ie, between matched dollar-signs), these synonyms are disabled, and only the mathematical symbols and Greek letters work.

Mathematical text
-----------------

Subscripts
..........

As in TeX and LaTeX, you must be in math-mode to use subscripts; in other words, you must enclose the string or substring in dollar-signs.  For single-character subscripts, insert an underline prior to the character to be subscripted:

     draw title "$a_2$"

For multiple-character subscripts, insert braces before and after the item to be subscripted:

     draw title "$a_{22}$"

Superscripts
............

As in TeX and LaTeX, you must be in math-mode to use superscripts; in other words, you must enclose the string or substring in dollar-signs.  For single-character superscripts, insert a carat prior to the character to be superscripted:

     draw title "$a^2$"

For multiple-character superscripts, insert braces before and after the item to be superscripted:

     draw title "$a^{22}$"

Mathematical symbols
....................

As in TeX and LaTeX, you indicate mathematical symbols and Greek letters with backslash sequences.  The following LaTeX symbols are defined in math mode in Gri (cf tables in Lamport's section 3):

     \Delta \Downarrow \Gamma \Im \Lambda \Leftarrow
     \Leftrightarrow \Omega \Pi \Phi \Psi \Re
     \Rightarrow \Sigma \Theta \Uparrow \Upsilon \Xi
     \alpha \approx \ast \beta \bullet \chi \circ
     \cong \delta \div \downarrow \epsilon \equiv
     \eta \exists \forall \gamma \geq \gg \in \infty
     \iota \kappa \lambda \langle \leftarrow
     \leftrightarrow \leq \ll \mu \nabla \neq \nu
     \omega \partial \phi \pi \pm \prod \propto \psi
     \rangle \rho \rightarrow \sigma \sim \subset
     \subseteq \sum \supset \supseteq \surd \sqrt
     \tau \theta \times \uparrow \upsilon \varpi
     \wedge \xi \zeta \vartheta \varsigma \varphi
     \aleph \oplus \otimes \wp \prime \emptyset
     \angle \neg \clubsuit \diamondsuit \spadesuit
     \cdot \lfloor \lceil \rceil \rfloor

For example, you might use these as follows:

     draw title "$\alpha$ = thermal expansion coefficient"

Sometimes you'll want a mathematical symbol to be adjacent to a normal text string, with no space between.  You can do this by enclosing in braces, as in LaTeX.

TeX and LaTeX handle combinations of superscripts and subscripts very cleanly, putting one above the other.  Presently, Gri does not do this; for example set x name "$A_1^2$" will have the 2 appearing to the right of the 1 instead of above it.  Proper positioning will be added to a later version of Gri, but in the meantime you can achieve the desired effect with the TeX ``negative thinspace'' psuedo-character in math-mode.  Using this feature will not hurt you when the new Gri becomes available.  The symbol for a negative thinspace is \! in math-mode.  It has no meaning in nonmath mode.  A thinspace is 1/6 of an ``em-space'' (a TeX term, normally equal to the width of the character ``M'' in the current font).  In most fonts, numbers are half the width of the letter ``M'', so that 3 negative thinspaces will move leftward over a single number.  Thus, if the example above becomes set x name "$A_1\!\!\!^2", the 2 will be positioned above the 1. (Equivalently, you could write set x name "$A^2\!\!_1$".) Depending on the actual characters you have in the super/subscripts, you might need more or less thinspaces; some experimentation might be required.  Also, note that the symbol \, in math mode is a positive thinspace (which moves the next character a little bit to the right).  Thus, you can add a little extra spaces between characters by doing something like set x name "A$\,$B".

To get a hat over a single character, do something like the following (which draws a hat over the character "h"):

     draw label "h${\!\!\!^{^\wedge}}$" at 10 12 cm

To get an overbar on a rho, do this:

     draw label "$\rho\!\!\!\!^-$" at 3 3 cm

Non-English characters
----------------------

Gri relies on the ``standard'' PostScript fonts, however, and it suffers all limitations of these fonts.

Gri supports both English and some other European-derived languages, permitting text with accents on letters.  (It does not support Oriental or other languages at this time.)  The accents are supported by using the so-called ISO-Latin-1 font-encoding scheme (also called the ISO-8859-1 scheme), and so, from what the author can gather from his reading, Gri should support various languages from western European, e.g. English, French, Spanish, Catalan, Basque, Portuguese, Italian, Albanian, Rhaeto-Romanic, Dutch, German, Danish, Swedish, Norwegian, Finnish, Faroese, Icelandic, Irish, Scottish, and as well as Afrikaans and Swahili.

Gri uses the ISO-Latin-1 font encodings by default, although the so-called `standard' font-encoding may also be selected with the Set Font Encoding command (Set Font Encoding).  For more on font encodings see any book on PostScript fonts ... although the bottom line is that if you are using accented characters in your work, then you probably already know about encodings, and if you don't use accents then you needn't learn about this topic except for the pleasure of learning about other languages.

The method of handling accented characters is very simple.  If you can type it, Gri can draw it!  It is up to you to determine how to enter the accents.  Most text editors permit this.  Since many users will prefer the Emacs editor, a few words about that are in order.

For complete information about entering iso-latin-1 characters in Emacs, consult your Emacs manual in the section (emacs)Single-Byte Character Support which describes the available methods suitable for the Emacs version you are using.  A few examples are nevertheless provided below.

Consider the task of inserting French text, with the Emacs text-editor. There are several ways of doing this (and you may wish to consult your emacs info manual).  A method that works in emacs-19 up to current emacs-20 versions uses the emacs iso-transl.el package by putting the following in your ~/.emacs file:

     (require 'iso-transl)
     (iso-transl-set-language "French")
     (standard-display-european t)

Loading the iso-transl package defines three ways of entering the non-ASCII printable characters with codes above 127: the prefix C-x 8, or the Alt key, or a dead accent key.  For example, you can enter uppercase A-umlaut as C-x 8 " A or Alt-" A (if you have an Alt key) or umlaut A (if you have an umlaut/diaeresis key).

A more recently introduced method is to enter the mode which allows quick insertion of iso-latin-1 characters. Do the Emacs command M-x iso-accents-mode (either manually, or in a hook that's done automatically). Now, suppose the x-axis is to represent temperature. All you'd have to do is type in the command

     set x name "Temp'erature"

As you type, the quote mark will dissappear, and reappear as an accent on the e.  And then, Gri will recognize this accented é, and it will draw the accent on the axis label.

Perhaps the future default way of accomplishing this task is to use MULE support directly.  First, customize MULE using M-x customize-group RET mule setting the current language environment (e.g. latin-1) and the default input method (e.g. latin-1-prefix).  Then, invoking M-x toggle-input-method (e.g. C-\) toggles into a mode similar to the iso-accents-mode minor-mode described above.

Adjustment Of Character Position
--------------------------------

Micro-positioning is available within math-mode, via the symbols \! (which means go left one thin-space) and \, (which means go right one thin-space).  (A thin-space is 1/6 the width of the letter ``M'').

Adding new commands to Gri
==========================

Gri provides so-called "newcommands" as a sort of subroutine syntax on steroids.

Purpose of newcommands
----------------------

Gri can be extended easily.  Primitive commands (e.g. set x name) can be supplemented with so-called "new commands."  New commands are a little like subroutines other programming languages.  For example, you might find that you often draw filled curves with a particular graylevel (say 0.5), and then return the graylevel to the previous value.  This requires you to do the following each time:

     new .old_graylevel.
     .old_graylevel. = ..graylevel..
     set graylevel 0.5
     draw curve filled to 0 y
     set graylevel .old_graylevel.
     delete .old_graylevel.

This gets a bit tedious, and it would obviously be nicer to just say something like

     Draw my kinda curve

To make this shortcut, you'd tell Gri about the existence of a new command called Draw my kinda curve, and tell it that the new command can be accomplished by the longer code fragment written above.

Once you've learned how to make new commands, you are likely to use them a lot.  The following explains how you add new commands.  For advice on programming style, etc., (Resource File).

How Gri parses commands
-----------------------

Whenever Gri reads a command line, it compares it with its list of commands.  This list is searched in this order: (1) the universal gri.cmd file (Invoking Gri), (2) your resource file (Resource File), if it exists, and then (3) your command file itself.  Gri stops searching when it finds a Gri command that matches the command line.  "Matching" means that the command line is identical in all words in a Gri command, scanning from the left, until it encounters a word containing

  * A quote (e.g. "string")

  * A synonym name (e.g. \file)

  * A variable name (e.g. .number.)

  * An opening square bracket (e.g. [option])

  * An opening brace (e.g.  {a|b})

  * A choice between two items (e.g.  first|second)

  * A variable-name with a & character immediately to the left (e.g. &.var.).  This is a signal that the variable may be changed inside the newcommand (The Ampersand Syntax).

  * A synonym-name with a & character immediately to the left (e.g. &\syn).  This is a signal that the synonym may be changed inside the newcommand (The Ampersand Syntax).

When Gri finds a command that matches your command line, it assumes that this is the intended command, and searches no further.  This means that you must be careful not to have your command hidden by other commands. For example, if your resource file contained these lines, Gri would never execute the second new command, because calls to it match the first command.  To avoid this, you may either reverse the order of the definitions, so that Gri will find the proper routine, or rename one of the routines.

     `Draw foo'
     Draw a foo.
     {
       show "drawing a foo"
     }
     `Draw foo bar'
     Draw a foo bar.
     {
       show "drawing a foo bar"
     }

Gri searches the gri.cmd file first, so any new command that you create that clashes with built-in commands will be ignored by Gri (Invoking Gri).  Gri will warn you of this, and proceed, ignoring your newer definition.  To get around this, you can use capital letters to begin the words of your new command.  By convention, Gri never uses capital letters in this way, so a clash is impossible (except with any similar command you might have defined previously, such as in your ~/.grirc file).

Simple example of a new command
-------------------------------

To make a new command called Show The Time insert the following into your ~/.grirc resource file or into your command-file somewhere near the top, or at least before you use the command.

     `Show The Time'
     New command to show the time of day.
     {
       show "\.time."
     }

EXPLANATION:

  * The name of the new command is enclosed in angled single-quote marks. The words of the new command should begin with upper-case letters to prevent a name clash with a present or future built-in Gri command. Formatting convention: Make sure that the entire definition string, from the opening angled quote to the ending angled quote, appears on one line.  Otherwise Gri will give an error like

          ERROR: Can't extract syntax for new command

  * Following the name line, you may optionally insert any number of lines which will become the help information for the new command.  See the file gri.cmd for the recommended stylistic conventions in writing help information (Invoking Gri). If your help text includes an example that uses an opening brace ({) you must escape the brace with a backslash, e.g. (\{).

  * Following the help lines, if they exist, the body of the new command is given, sandwiched between a starting line containing an opening brace ({) as the only nonwhite character, and an ending line containing a closing brace (}) as the only nonwhite character. Any valid Gri commands may be used in the body of the new command.  It is acceptable to use other new commands in the body. Recursion is also allowed -- a new command is allowed to call itself (although there is a limit on nesting, of perhaps a thousand or so; this varies with the version of Gri).  Formatting convention: It is usual, but not necessary, to use an indentation level of 2 spaces in the body of the new command.

The new command is invoked by Show The Time.  Help for the command is found by help Show The Time or help Show.

Complicated example of a new command
------------------------------------

The following example from the global gri.cmd file illustrates how to parse/check the commandline (Local Synonyms), which is a good practice in any code you expect to re-use.  The first if statement checks that the word at is in the right place (this would not have been checked by the syntax matcher, the word having followed a string).  The presence of the keyword cm is checked for, and user units or cm units are used accordingly.  Local variables are created (new) and then destroyed (delete) so that this new command cannot affect outside code.

     `draw label whiteunder "\string" at .xleft. .ybottom. [cm]'
     Draw label for plot, located with lower-left corner
     at indicated (x,y) position (specified in user
     units or in cm on the page).  Whiteout is used
     to clean up the area under the label.  BUGS:
     Cannot handle angled text; doesn't check for
     super/subscripts.
     {
         if {rpn "\.word4." "at" !=}
           show "ERROR: 5th word must be `at', not `\.word4.'"
           show traceback
           quit
         end if
         new .x. .y. .oldgray. .space.
         if {rpn \.words. 7 ==}
           .x. = {rpn \.word5. xusertocm}
           .y. = {rpn \.word6. yusertocm}
         else if {rpn \.words. 8 ==}
           if {rpn "\.word7." "cm" !=}
             show "ERROR: Require 8th word to be `cm'"
             show traceback
             quit
           end if
           .x. = \.word5.
           .y. = \.word6.
         else
           show "ERROR: Require 7 or 8 words, not \.words."
           show traceback
           quit
         end if
         # Coordinates now in cm.  Next, white out a box
         # under the text (and .space. centimetres
         # beyond text), then draw label.
         .space. = 0.1               # Space of 1mm
         .oldgray. = ..graylevel..
         set graylevel white
         draw box filled                          \
           {rpn .x. .space. -}                    \
           {rpn .y. .space. -}                    \
           {rpn .x. "\.word3." width + .space. +} \
           {rpn .y. "M" ascent + .space. + } cm
         set graylevel .oldgray.
         draw label "\.word3." at .x. .y. cm
         delete .x. .y. .oldgray. .space.
     }

Altering command arguments -- the & syntax
------------------------------------------

The Gri language permits a newcommand to change variables and synonyms passed as arguments, using a syntax that is quite similar to that employed by the C++ language.

Overview of the & syntax
........................

Normally the arguments to a newcommand are parsed into either numerical values or strings, before execution is passed into the newcommand.  This is a akin to the scheme called "call by value" in some programming languages.  Gri also provides a syntax, borrowed from C++, that permits a newcommand to alter the contents of variable or synonym arguments.

The technique is simple.  To permit a newcommand to modify an argument that is a variable or a synonym, just put a & to the left of the item on the calling line.  Then, within the newcommand, the corresponding local synonym (i.e. \.word1., etc.) will behave as though it were the instance of the original variable or synonym.

The & is placed to the left of the variable-name or synonym-name without intervening space.  For example foo &.var. &\syn tells the parser that the newcommand named foo may possibly alter the values of the variable .var. and the synonym \syn, as they exist in the calling context.

It is important to note that Gri pays very little attention to the & in a syntax-declaration line.  All it does is to note that the item to the right of the & is not a fixed word in the newcommand being defined; this follows the usual rules for parsing newcommand syntax (Parsing).

Example: doubling a variable
............................

Consider the task of adding a fixed amount to a variable.  If the variable we wish to double is .x., we might write

     `double_a_particular_variable'
     {
         .x. = {rpn .x. 2 *}
     }
     .x. = 10
     double_a_particular_variable

Code such as that presented above occurs in many applications.  (Turn the multiplication into an addition, and change .x. to ..ymargin.., and you'll start to see the core of an application that draws multiple graph panels, one above another.)  However, the code is too specific to be of much general use!

What if we want to double some other variable instead?  The code below shows how to do that.

     `double &.value.'
     {
         \.word1. = {rpn \.word1. 2 *}      # line 3
     }
     .x. = 10                               # line 5
     double &.x.
     .y. = 3.14
     double &.y.

At line 3 Gri interprets the \.word1. to the left of the equals sign as a reference to the variable that is set to the value 10 in line 5.  Similarly, the \.word1. to the right of the equals sign evaluates to 10, the value in the calling program.

Gri automatically determines whether an item is a variable or a synonym, and does the correct thing.  Thus, for example, if line 3 above were written as

     \.word1. = "hello"                 # ERROR

an error would be reported, since double was called with a variable as an argument, and variables cannot hold strings.

Example: manipulating a synonym
...............................

Synonyms are treated in the same way, as is illustrated in the following example.

Q: what does the following print?

     `add_a_dat &\filename'
     {
         \.word1. = {rpn "\.word1." ".dat" strcat}
     }
     \filename = "test"
     add_a_dat &\filename
     show "\filename"

A: it prints test.dat.

Nesting
.......

One newcommand may call another, letting a deeply-nested newcommand alter values of synonyms and variables that may otherwise be hidden behind new items of the same name.  This is done by using the & notation at each step.  The following provides an example of passing a variable through two levels of newcommands.

Q: what does the following print?

     `food critic &food'
     {
         \.word2. = "\.word2.s"
         yummy &\.word2.
     }
     `yummy &foods'
     {
         \.word1. = "\.word1. are tasty"
     }
     \a = "apple"
     food critic &\a
     show "\a"

A: it prints apples are tasty.

About new and delete
....................

If new and delete are executed on local synonyms inside newcommands (e.g.  new \.word1.)  they create and destroy variables and synonyms in the context of the calling program.

For example, consider the following.

Q: what does the following print?

     `poetry &\s'
     {
         new \s                             # line 3
         \s = "rose"
         \.word1. = "\.word1. is a \s"      # line 5
         delete \s                          # line 6
     }
     \s = "A rose "                         # line 8
     poetry &\s
     show "\s"

A: it prints A rose is a rose.

The key point here is that the instance of the synonym named \s in the calling program, set in line 8, is modified by the poetry newcommand, in line 6.  This modification involves the use of a synonym, also named \s, that "lives" wholly within the newcommand, being created in line 3 and destroyed in line 6.

Determining calling information
...............................

Newcommands may determine the name and the nesting level of changeable calling arguments.  To get the name, put a single ampersand after the backslash of the local synonym of interest.  To get the nesting level (0 for main program, etc.) put two ampersands after the backslash.

     `NC &.var.'
     {
         show "\&.word1. (expect '.a.')"
         show "\&&.word1. (expect 0)"
     }
     .a. = 1
     NC &.a.

Note: neither of these items may be used an lvalue.  That is, they may not be used to the left of an equals sign.  But you can always get around that by clever use of alias synonyms (Alias Synonyms).

How Gri implements the & syntax
...............................

When the parser encounters an unquoted & followed immediately by the name of a variable or a synonym, it converts the whole token (& plus name) into a specially-encoded string that can be recognized inside newcommands.  (This is only done if the & and the variable name are not enclosed in double quotes.)

This specially-encoded string contains not just the name of the variable or synonym, but also the current level of nesting of newcommands.  In this way a newcommand can have its own private versions of variables, created by new, that won't be misinterpreted for the identically-named variables in the calling program.

The format of these specially-encoded strings is #\bn\ba\bm\be\b:\bN \b_ \bl\be\bv\be\bl\b:\bL#\b, where N stands for the name of the variable/synonym, L stands for the current level, and \b is the backspace character (hexadecimal 08 in the ascii table).  This string is designed to be strange enough that users are unlikely to use it themselves.  The coding scheme is not entirely arbitrary, however; note that if the backspace characters are ignored the result has the form name:N_level:L.  It's also worth noting that if this string were printed on a terminal that erased characters when typing backspaces the result would be of the form N_L.

Examples: .a. in the main program (i.e. at level 0) encodes to #\bn\ba\bm\be\b:\b.a. \b_ \bl\be\bv\be\bl\b:\b0#\b and &\my_syn inside a newcommand called by the main program (i.e. at level 1) encodes to #\bn\ba\bm\be\b:\b\my_syn \b_ \bl\be\bv\be\bl\b:\b1#\b.

Inside a newcommand, Gri checks to see if builtin synonyms (e.g. \.word1.) hold such specially-encoded strings.  If so, then the appropriate versions of the variables are used in preference to any variables that may have been newly created by new inside the newcommand.

Hints for Gri Programming
=========================

Here are some hints for good Gri programs:

  * Whenever working with grids (for contouring) or images, make use of the show grid or show image commands.  They will give you useful information about the statistics (min/max/histogram) of the items.

  * Use the operating system, not Gri, to manipulate your data.  For example, if you have a file whose first column is x times 100, and third is the arcsin of y, you could do:

          open "gawk '{print $1/100, sin($3)}' |"
          read columns x y

     If you have x and y in a non-decimal geographical format (e.g. hour.minute-second format), use the operating system to convert for you (Open).

  * Use the pstack operator liberally in your rpn expressions to see what is going on (rpn Mathematics).

  * While developing programs, put a show columns statistics command after every read column command, to check that the data have been read correctly.

  * Development time can be minimized by limiting the number of data being processed.  For example, in a multi-panel plot, it is often necessary to try various alternatives before aesthetic scales and page layout is achieved.  The process can be speeded up by limiting the number of data being processed, as shown below.  (If Gri finds fewer data in the file than specified, it will simply use the data that it found; so when the program works, just change .n. into something large.)

          .n. = 100 # 10000 for later
          ...
          # Panel 1
          read columns .n. x y
          ...
          # Panel 2
          read columns .n. x y
          ...

  * Create new commands to do repetitive work.

  * Use draw time stamp on all plots except for publication versions:

          if !..publication..
            draw time stamp
          end if

  * For multiple panels on one page, do delete x scale or delete y scale before each new panel, so you will start afresh.  Clearly identify code for particular panels with comments.  This reduces errors you might get if you shuffle things later.

  * Use the ..num_col_data.. built-in variable to see how many data have passed the set input data window data window in the last read columns command.  The following example shows how to avoid drawing an unwanted curve:

          open \f
          read columns x y
          close
          if ..num_col_data..
            draw curve
            draw label "\f" at \
                {rpn ..xlast.. xusertocm 0.5} \
                {rpn ..ylast.. yusertocm 0.2} cm
          end if

  * Use synonyms and query for filenames.  This makes programs much more flexible.  Note that you can string synonyms together:

          \dir = "~/EOS/iso0/"
          query \file "Give file in directory \dir" ("1.dat")
          open \dir/\file

     It is also a good idea to give a restrictive list of possibilities in your query command, to avoid complicated if commands later (Query).

  * Use multiple draw title commands:

          draw title "Atlantic water entering Arctic Ocean"
          draw title "\.command_file. \.time."

  * Use the query command to interact with the user (Query).  The results can be stored in variables and synonyms.

Debugging Gri Programs
======================

Here are some hints for debugging Gri programs:

  * If no data appear on an xy plot, insert show columns statistics or show columns after the read columns command.  It may be that you have fixed your axes, and that the axes frame does not include the data.

  * If you get an error message, rerun your Gri program using the -trace command-line option, to see which line is causing the problem.  This often reveals logic errors (e.g. in (if statements).  You may also turn tracing on or off at any point in your Gri program by setting the built-in variable ..trace.. to 1 or 0. Many Gri users have the Gri command aliased to be in trace mode by default.

  * If Gri complains of a syntax error, consult the printed manual, one of the online manuals, or the online help facility (Online Help).

  * Check the version number (printed at startup) to see if a new version of Gri has been installed, and check the manual for known incompatabilities.

  * Sprinkle show commands throughout your program, to see what's happening.  Even when you are sure your program works, it is a good idea to embed show statements so are they executed if the -debug flag is set:

          if ..debug..
            show "X=" .x. "and label is `\label'"
          end if

  * If your draw commands don't draw anything, check to see whether you've fooled yourself by enforcing an improper scaling; remove explict scaling (set x axis ...), clipping (set clip), data selection windows (set input data window x|y) and missing values (set missing value).  Another trick is to read only a portion of the data set (read columns 10 x y) and then print out all the values (show columns).

If you determine that the bug is in Gri, not in your program, please report the bug, so that other users will not have the same hassle; (Reporting Bugs).

Error Messages
==============

Gri error messages are in three types:

 1. Operating system error messages, such as segmentation fault. These should never appear, and indicate a bug in Gri.  Please report these to the author (Reporting Bugs).

 2. Internal Gri error messages.  The message starts with the words FATAL error, and quotes a file number and a line number, e.g.

          FATAL error: startup.c:199: ...

     Such errors indicate either a deficiency in your computer (e.g. insufficient storage space) or an internal bug in Gri.  If the message does not indicate running out of storage, please report the error to the author (Reporting Bugs).

     For fatal error messages on a unix system, Gri dumps core, unless you have turned that feature off, with the ulimit -c 0 unix command in a startup file.  This creates a file called core, which can help you in diagnosing the Gri bug.  If you have the gdb debugger, just type gdb gri core and then type where to get a traceback stack.  Please email this with your other information about the Gri bug.

 3. An indication that your commandfile is flawed, either in syntax or in meaning.  These messages end with a line indicating the offending line in your commandfile, e.g. the command set x axis 0 1 -1 yields:

          ERROR: `set x axis .left. .right. .incBig.'
                  has .incBig. of wrong sign
           Bad command:  `set x axis 0 1 -1 '

     Normally, such error messages do not indicate a flaw in Gri, but rather in your reasoning, so report them to the author only if you are very sure that a Gri bug must underly them.

Missing data
============

Most Gri commands will ignore data points equal to a "missing value." For example, draw curve connects only points which are not equal (to within 0.01 percent) of the missing value.  The curve has holes at missing data.  Initially the missing-value is set to 1.0e22.  You may alter this value with set missing value .value.. The built-in variable ..missingvalue.. stores the current value of the missing-value.

Additionally, Gri will ignore anything it reads that is equal to the string NaN or Inf.  These are produced by matlab, C, and other programs when dividing by zero, etc.

Gri also ignores mathematical operations on data items which are equal to the missing value.  Thus, for example, if your missing value is -99 then the command x += 1 will not change the values equal to -99 to -98, since this would have the side-effect of making the datum no longer be considered missing.

Interaction Between Gri and Operating System
============================================

Using the OS from within Gri
----------------------------

Gri uses the operating system internally for things like paging through help information.

The operating system may be called within Gri commands, using a syntax borrowed from the Bash unix shell.  After substituting synonyms in the commandline, Gri scans for dollar-parenthesis blocks (e.g. \$(system-command), replacing them with the textual result of sending the indicated system-command to the OS.  The replacements are done from left to right in the commandline, starting at the deepest nesting level.

Often the dollar-parentheis syntax is used in title commands, to indicate the full pathname of the Gri commandfile, e.g.

     draw title "\$(pwd)/\.command_file."

In assignment to synonyms, expansion of dollar-parenthesis is not done. Thus the operating system is called twice on the second line below, and not at all on the first line; to see this, run it as gri -s8 -t.

     \dir = "\$(echo $MY_DIR)"
     show "\$(head -1 \dir/MY_FILE)"

Syntax Note Dollar-parenthesis blocks must be prefixed with backslash to avoid confusion with math expressions within strings, for example to avoid breaking draw label "$(x,y)$" at 3 3 cm.  This is an example of how TeX notation and unix shell notation collide.

Example It is a good idea to employ unix environment variables to name directories containing data, so that Gri scripts will work unchanged even if the data are moved (so long as the environment variables are altered), e.g.

     # Figure how many lines in a file
     \dir ="$(echo DIRECTORY_WHERE_I_STORE_SOLAR_DATA)"
     open "\dir/solar_data_file_name`
     ...
     open "\$(echo DIR_ANOTHER)/another_data_set"

Another method is to pass instructions to the operating system with the system command.  This discards output.  Whatever follows the word system is first scanned for synonyms (but not rpn expressions or variables); after replacement of any existing synonyms, the line is passed directly to the operating system.  Any results are printed on the terminal.

Frequently used system commands are awk, head, grep and sed.  Examples:

  * Here's how to paste several files together to form a temporary file for plotting.  (Notice that a temporary file incorporating the PID of the job is created and later removed.)

          system paste -d" " 1.dat 2.dat 3.dat > tmp.\.pid.
          open tmp.\.pid.
          read columns x y
          close
          system rm tmp.\.pid.

  * Here's how to plot each line in a file called inp which has the string ; at the start of the line.

          system cat inp | grep -v "^;" | cat > tmp.\.pid.
          open tmp.\.pid.
          read columns x y
          system rm tmp.\.pid.

  * Here's how to use the awk system command to create a tabulated function for plotting.

          system awk                             \
              'BEGIN {                           \
                 for (x=0; x<1; x+=0.1) {        \
                   printf ("%f %f\n", x, sin(x)) \
                 }                               \
               }'                                \
              > tmp.\.pid.
          open tmp.\.pid.
          read columns x y
          close
          system rm tmp.\.pid.
          draw curve

     This example is more cleanly written using the piping facility of the open command (which automatically creates a temporary file, and destroys it when close is done)

          open "awk 'BEGIN {       \
            for(x=0;x<1;x+=0.1) {  \
              print(x,sin(x))      \
            }                      \
          }'|"
          read columns x y
          close
          draw curve

  * Sometimes you need just a single output item from the operating system.  In this case, you can store the results from the operating system in a synonym by using the \synonym = system ... assignment command.

  * subroutine A related command is \synonym = tmpname, which stores in the synonym the name of a temporary file created by the system.  The file is created with the tmpname system call, so it is guaranteed not to clash with any existing files.  Typically, the filename is something like /usr/tmp/griAAAa1233.  In many cases you'll want to remove the file within Gri, once you're done, and that can be done with unlink (Unlink) or with a system rm -f command.  A useful bit of code is as follows

          \file = tmpname
          system ... SOME_SYSTEM_COMMANDS ... > \file
          ... use this new file for something ...
          unlink \file

Using Gri from within the OS
----------------------------

This section only applies to unix systems.

Save the following into a file called p and then make it executable using chmod.  It runs Gri on a named file, with the -yes flag set so that any query commands are automatically answered in the affirmative, and then displays the results in a Ghostscript window. (USAGE: p cmdfile.gri)

     #!/usr/bin/sh
     # Run Gri, then plot in gs window
     case $# in
     1)
             base=`basename $1 .gri | sed -e s/.*,#`
             gri -yes $base.gri && ghostview $base.ps
             ;;
     *)
             echo "Proper usage: $0 cmdfile.gri"
             ;;
     esac

Sample Resource File
====================

The following shows a sample ~/.grirc resource file.  Much of the code here is adding new commands (Adding New Commands.)

     # Some folks like tics to point inwards ...
     set tics in

     # Hey, I'm bored with Helvetica font, and
     # Palatino is a bit prettier than Times
     set font to PalatinoRoman

     # Now for something a bit less trivial.
     # This lets me draw a set of y-values
     # against a single x-value, by e.g.
     #    open xyyy.dat
     #    draw curves time T1 T2 T3
     # where the first column of the file is
     # time, and the others are temperatures
     # at various sensors.
     `draw curves \xname \y1name ...'
     Draw multiple y columns versus an x column.  Assumes
     that the datafile is open, and that x is in the first
     column, with the y values in one or more following
     columns.

     The number of columns is figured out from the options,
     as is the name of the x-axis, and the labels to be
     used on each of the y curves.
     {
       # NB. the 3 below lets us skip the words 'draw'
       # and 'curves', and the name of the x-column.
       .num_of_y_columns. = {rpn wordc 3 -}
       if {rpn .num_of_y_columns. 1 >}
         show "ERROR: `draw curves' needs at least 1 y column!"
         quit
       end if

       set x name {rpn 2 wordv}
       set y name ""

       # Loop through the columns.
       .col. = 0
       while {rpn .num_of_y_columns. .col. <}
         # The x-values will be in column 1, with y-values
         # in columns 2, 3, ..., of the file.
         .ycol. = {rpn .col. 2 +}
         rewind
         read columns x=1 y=.ycol.
         # At this point, you may want to change line thickness,
         # thickness, color, dash-type, etc.  For illustration,
         # let's set dash type to the column number.
         set dash .col.
         draw curve
         draw label for last curve {rpn .col. 3 + wordv}
         .col. += 1
       end while
     }

Environment
***********

Gri comes with a few ancillary programs that may be useful.  Gri also provides a simple scheme to use other system tools (e.g. awk). These are discussed here.  And speaking of discussing, this chapter ends with a note about a mail-list Gri discussion group.

Extra things provided with Gri
==============================

gri_merge -- combine PostScript files
-------------------------------------

Merge separate PostScript files, created by Gri, into one page.  To learn how it works, type gri_merge -h at the system prompt, to see:

     PURPOSE: Strings Gri PostScript files together.

     BUGS:    With old versions, of gri, make sure to match each `set clip
      postscript on' with a `set clip postscript off'.

     USAGE (style 1):
         gri_merge [OPTIONS] CxR a.ps b.ps ... > merged_file.ps
      Merges the files onto one page, in 'C' columns and 'R' rows.  The C*R
      files are given in the order of words on a page.  The page is
      presumed to be 8.5x11 in size, as are all the input files, and the
      input files are sized to fit, and kept in natural scale.

     USAGE (style 2):
         gri_merge [OPTIONS] xcm ycm enlarge a.ps [b.ps ...] > merged_file.ps
      Where `enlarge' is a scale factor applied after offsetting `xcm' to
      the right and `ycm' upward.

     EXAMPLE (style 2):
      The following
        gri_merge  2 12 .5 a.ps \
                 12 12 .5 b.ps \
                  2  2 .5 c.ps \
                 12  2 .5 d.ps > all.ps
      produces 4 panels from gri plots done using margins and sizes
      as specified in the following lines in a gri commandfile
        set x margin 2
        set x size 15
        set y margin 2
        set y size 15
      The OPTIONS, available if your 'perl' has 'getopts' library, are:
        -u graylevel -- set graylevel for underlay beneath panels, by default 0.75.
                        Values range from 0 (black) to 1 (white), although a value
                        of precisely 1 means do NOT draw underlay.
        -b graylevel -- Set value for background under individual panels, again 0
                        for black to 1 for white, with 1 meaning no drawing.
        -h           -- Print this help message and quit.

gri_unpage -- split pages into files
------------------------------------

Given a multipage PostScript file, gri_unpage creates several new PostScript files, one for each page.  To learn how it works, type gri_unpage -h at the system prompt, to see:

     PURPOSE: Chop multipage Gri PostScript file into one file per page.
     USAGE:   gri_unpage name.ps -- create files name-1.ps, name-2.ps, etc, one
                                    for each page of name.ps.
              gri_unpage -h      -- print this help message

     BUGS:    1. Bounding box is always 8.5x11 inches.
              2. Assumes that all Gri fonts are used even if they aren't.

Using System Tools With Gri
===========================

Using system tools to manipulate your data makes sense for several reasons.  First, you may be familiar with those tools already.  Second, learning these tools will help you in all your work.

Introduction
------------

Each of the programs listed in the sections below is available for Unix. Some (e.g. Perl and the Awk variant called Gawk) are available on other operating systems as well.  Each of these tools is fully documented in Unix manpages, so here I'll just give an indication of a couple of useful techniques you might want to use.

Bear in mind that these tools can do very similar jobs.  For example, Awk can do much of what Sed and Grep can do, but also a whole lot more. If you don't know Sed or Grep, I suggest you learn Awk instead.  Then again, Perl can also do anything Gawk can do, and a whole lot more! (For one thing, it is easier to work with multiple files in Perl.)  In fact, Perl is the most powerful of this list.  If you know none of these tools, you might want to learn Perl instead of the others.  But Perl is more complicated for simple work than Awk is, so the most reasonable path might be to learn both Awk and Perl.

For simple applications, you will probably want to use these tools in a piped open command, e.g.

     open "awk '{print $1, $3/$2}' MyFile |"

which creates a temporary file (automatically erased when Gri finishes) which contains the output from running the system command that preceeds the pipe symbol (|) (Open).

(Here and in all the examples of this chapter, it is assumed that the user's input file is named MyFile.)

For more complicated appplications, you may use the Gri system command as follows.

     system perl   >tmp  <<"EOF"
     open(IN, "MyFile");
     while(<IN>) {
         ($x, $y) = split;
         print "$x", " ", cos($y), "\n";
     }
     EOF
     open tmp
     read columns x y
     draw curve
     system rm -f tmp

Here a temporary file, named tmp, has been used to store the results of the calculation.  Note that this file was specifically cleaned up by the second system command.  (Many folks, including the author, would prefer to take the perl script out of the above and make it a standalone executable script, calling it from Gri with the one-line form.  But it is just a matter of style.)

Grep
----

The most common application of Grep is to select lines matching a pattern, or not matching a pattern.  Here is how to skip all lines with the word "HEADER" in them:

     open "grep -v 'HEADER' MyFile |"
     ...

Note that Gawk and Perl do this just as easily.

Sed
---

Sed is normally used for simple changes to files.  For example, if you have columnar data which are separated with comma characters instead of whitespace, you could make it Gri compatible by

     open "sed -e 's/,/ /g' MyFile |"

Where the -e flag indicates that the next item is a command to Sed, in this case a command to switch ("s") the comma character with the blank character, globally ("g") across each line of the file.  See also the overview of Perl.

Awk
---

Awk is great for one-liners.  If your system lacks Awk, you can procure the GNU version, called Gawk, from the web for free.  For better or worse, Gawk is not fully compatible with Awk.  The good thing is that Gawk is pretty much the same on all operating systems, whereas the installed Awk may not be.  I use Gawk instead of Awk, for this reason and because it is normally faster.

The main concept in Awk is of "patterns" and "actions."  In the Awk syntax, actions are written in braces following patterns written with no braces.  (This will become clear presently.)

Whenever a line in the data file matches the pattern, the action is done.

The default pattern is to match to every line in the file.  This is done if no pattern is supplied.

The default action is to print the line, and this is done if no action is supplied.

Here are a few examples.  To skip first 10 lines of a file:

     open "awk 'NR>10' MyFile |"
     read ...

Here the pattern was that NR (a special Awk variable for the number of the record, starting with 1 for the first line of the file) exceeded 10.  And the action was taken by default since nothing was supplied between braces, to print this line.

To plot the cosine of the second column against the first column:

     open "awk '{print ($1, cos($2))}' MyFile |"
     read columns x y
     draw curve

Here no pattern was supplied, so the action was done for every line.

Combining these two forms, then, and supplying both a pattern and an action, here is how one might print the first and eighth columns of the file MyFile, but only for the first 10 lines of the file:

     open "awk NR<=10 {print ($1, $8)} MyFile |"

Perl
----

Perl can do almost anything with your data, since it is a full programming language designed to also emulate several Unix utilities.

In perl, as in other commands, the commandline switch -e indicates that a Perl command is given in the next word of the command line.  The commandline switch -p indicates to print the line, after any indicated Perl actions have been done on it.  Here, for example, is how one would emulate a Sed replacement of comma by blank:

     open "perl -pe 's/,/ /g' MyFile |"

Perl also has a commandline switch -a indicating that lines should be "autosplit" into an array called $F.  The first element of this array is $F[0].  Splitting is normally done on white-space character(s), although this may be changed if desired. Here, for example, is how to take the cosine of the second column of a file, and print this after the first column:

     open "perl -pea 'print($F[0], cos($F[1]))' MyFile |"

Gri Discussion Group
====================

Before emailing to the Gri newsgroup, it is a good idea to consult the list of answers to Frequently Asked Questions.

As of summer 2000, Gri traffic has been moved to the web-based discussion groups at the SourceForge website http://gri.sourceforge.net about which little need be said here, because the website is very easy to use.

Editing Gri Files in GNU Emacs
******************************

If you use the GNU Emacs (or XEmacs) text editor, writing Gri command files is made easier with the Gri editing mode (gri-mode.el), written by Peter S. Galbraith <psg@debian.org>.

About Gri Mode
==============

Gri mode has all the wonderful things you've come to expect from Emacs modes. Here's a brief overview of the features:

  * It can complete partially typed commands, builtin variables and synonyms (gri-complete, M-Tab) and help you edit the syntax that was thus inserted for you (gri-option-select, C-c C-o; gri-option-kill, C-c C-k).

  * It can provide a short help synopsis concerning the command on the current line (gri-help-this-command, C-c C-h), or load the info manual for that command (gri-info-this-command, C-c C-i).  It knows the list of all Gri commands, and can provide help or info regarding any of them (gri-help, C-c M-h; gri-info, C-c M-i) using command name completion at the prompt (Tab).

  * All Gri commands are listed in a pull-down menu from the menubar, which you can use to either enter the text of the selected command, or obtain help or info about it.

  * It can help you find an unknown command by listing all containing a given word (gri-apropos, C-c C-a).

  * It fontifies your Gri code using colour coding.

  * It indents if statements, loops, and so on (gri-indent-line, Tab).

  * It can let you run Gri and view its output without leaving the editor (gri-run, C-c C-r).  If an error is encountered, Emacs will rearrange the buffer so the cursor is on the bad line of the Gri command-file.

  * If you've already run Gri, and therefore have a PostScript output file, the mode will let you view that file (gri-view, C-c C-v) even if that file is compressed.

Thus one never has to leave Emacs; type C-c C-r to run Gri, and if there is no error, the graph comes up automatically.  If there was an error, gri-mode will move editing point to the line with the error and display the error message. Given that the mode can complete partially typed commands, this means a substantial saving in development time.

Inside gri-mode, type C-h m for help on the mode, including a list of all commands and key definitions.

Gri-mode screenshots, what it looks like.
=========================================

Screenshot 1
------------

Screenshots are not visible in the info node; see the online HTML documents.

In the first screenshot, the user has entered the text set font and has pressed M-Tab twice to see the list of possible completions.  The *Completions* buffer is displayed in a separate frame because the user is using the framepop.el add-on package.  A similar effect can be obtained using special buffers in Emacs.

Screenshot 2
------------

Screenshots are not visible in the info node; see the online HTML documents.

Here, the user has selected the command set font to and, forgetting what valid font name could be used, then invoked C-c C-h to get help about that command. The user found the needed information and finished typing in `Courier'. Meanwhile, an idle timer displays the default setting for this command in the minibuffer after a few seconds of inactivity.

Screenshot 3
------------

Screenshots are not visible in the info node; see the online HTML documents.

Here we see the user cascading through the Gri commands pull-down menu until draw axes is reached.  This menu can be used to display Info (or help) about a given command, or to insert the selection.  The default is Info.  This menu is a good way to browse for a command when you don't exactly remember its name.

Screenshot 4
------------

Screenshots are not visible in the info node; see the online HTML documents.

With the output previewed in a gv window after pressing C-c C-v (or pressing the gv icon in the toolbar, or selecting it from the Perform pull-down menu), the user is ready to print the file, here using the Perform pull-down menu.

Installing gri-mode.el, the nuts and bolts.
===========================================

The Emacs gri-mode.el file is now bundled with gri, so odds are you already have it.  If not, you will find it at gri's web site http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/gri/gri/gri-mode.el

The following installation steps appear a bit complicated. That's only because gri has changed how it gets installed a few times, and gri-mode.el works with all of these various methods.  If you use gri from a Linux package (Debian or Red Hat) or if you compiled it yourself using the default configuration, you won't need to do much.

To install gri-mode.el, follow these 4 steps.  If gri-mode is already installed, you can skip the first two steps and move on to the last two, in which you tell Emacs that you'd like to use Gri mode when you edit files that end in .gri, the Gri suffix.  (Actually, if you're using Debian linux, you can skip all of these steps since the system will assume that you want gri-mode if you're editing a Gri file.)

Placing gri-mode.el where Emacs can find it.
--------------------------------------------

(Those using gri from gri's RPM package, a Debian package or a Red Hat package users can skip this, as it is done for them)

Extra .el files like gri-mode.el that are not part of Emacs should be stored in a directory where Emacs will find them when you ask it to load them.  The files should therefore be found in Emacs' load-path.  To see the directory list currently in the load-path, do this in Emacs:

     C-h v load-path

If you have access to system directories, put gri-mode.el in a site-lisp directory, such as /usr/local/share/emacs/site-lisp/ That way all users will have access to the files.

If you don't have access to a site-lisp directory (e.g. you have only a user account), then create a directory where your extra .el files will be stored and add it to Emacs' load-path.  For example, say you created the directory ~/emacs and stored gri-mode.el there, you would then put this near the top of your ~/.emacs file:

     (setq load-path (cons "~/emacs" load-path))

Telling gri-mode where gri resides
----------------------------------

(Those using gri from gri's RPM package, a Debian package or a Red Hat package users can skip this, as it is done for them)

You may skip this section if gri is installed on your system as /usr/local/bin/gri-2.12.23 and /usr/local/share/gri/2.12.23/gri.cmd (the default when compiling gri yourself).  If not, then you may need to set the Emacs variable gri*directory-tree in a startup file such as in your ~/.emacs file.

The Emacs variable gri*directory-tree is used to configure gri-mode to tell it where Gri is installed on your system. For the default gri installation paths used in this gri release, gri-mode expects to find the gri executable and the file gri.cmd as: gri*directory-tree/2.12.23/gri.cmd and /usr/local/bin/gri-2.12.23 where gri*directory-tree is by default set to /usr/local/share/gri/.

If you have only one version of gri installed on your system, gri-mode will also look to find gri.cmd and the gri executable like so:

 1. Gri executable in the PATH, with startup file gri*directory-tree/gri.cmd.

 2. Gri executable in the PATH, with startup file gri*directory-tree/lib/gri.cmd.

 3. Gri executable gri*directory-tree/bin/gri, with startup file gri*directory-tree/lib/gri.cmd.

However, gri-mode was designed to support, and ease the use of, multiple installed versions of gri.  To use this feature, you must use the gri version number as a directory name under the gri*directory-tree path, like this:

     gri*directory-tree/VERSION/bin/gri
     gri*directory-tree/VERSION/lib/gri.cmd

(e.g. /opt/gri/2.040/bin/gri and /opt/gri/2.040/lib/gri.cmd with gri*directory-tree set to "/opt/gri")

or without the lib and bin subdirectories if the executable is found in the PATH named like gri-VERSION (This is the way Debian packages are set up): the file gri*directory-tree/VERSION/gri.cmd and the gri-VERSION executable in the PATH (e.g. /usr/share/gri/2.1.18/gri.cmd and /usr/bin/gri-2.1.18 with gri*directory-tree set to "/usr/share/gri")

Important note: You may have more than one tree and make a list of them:

     (setq gri*directory-tree '("/opt/gri/" "/usr/share/gri/"))

Examples:

 1. If you use a RedHat package installed like:

          /usr/bin/gri
          /usr/share/gri/gri.cmd

     then you'd also use:

          (setq gri*directory-tree "/usr/share/gri/")

     but gri-mode would know of only one installed version of gri.

 2. If you use a Debian GNU/Linux installation like:

          /usr/bin/gri -> /usr/bin/gri-2.1.18
          /usr/share/gri/2.1.18/gri.cmd

     then you'd use:

          (setq gri*directory-tree "/usr/share/gri/")

     Note that all gri binaries must exist in the path with version number suffixes (e.g. gri-2.1.18) since there is no /usr/share/gri/2.1.18/bin/ directory (using a similar structure to opt/gri below) where gri-mode can find the binary corresponding to a given version number.

 3. If you had multiple versions of Gri installed like so (this reflects the installation paths used in older gri releases):

          /opt/gri/2.040/bin/gri
          /opt/gri/2.040/lib/gri.cmd
          /opt/gri/2.041/bin/gri
          /opt/gri/2.041/lib/gri.cmd

     then you'd use:

          (setq gri*directory-tree "/opt/gri/")

Telling emacs to load gri-mode
------------------------------

(Those using a Debian package can skip this, as it is done for them)

To tell emacs to use this mode with .gri files, you can load gri-mode whenever a new emacs session is starting by adding the following line to your ~/.emacs file:

     (require 'gri-mode)

This is a good method when you only start emacs once a week and use it for every file you edit (as you should).

If you startup a fresh emacs every time you edit then you probably only want to load gri-mode into emacs when you need it.  In that case, instead of the require statement above, add the following lines to your ~/.emacs file:

     (autoload 'gri-mode "gri-mode" "Enter Gri-mode." t)
     (setq auto-mode-alist (cons '("\\.gri$" . gri-mode) auto-mode-alist))

The first line tells Emacs that it will find out what it needs to know about running the command M-x gri-mode by loading the file gri-mode.el.  The second line tells it to run the command M-x gri-mode when a file with extension .gri is visited (thus using gri-mode with all those files).

Extra user configuration of gri-mode
------------------------------------

All users should do this at some time.

At this point, gri-mode should start up when you edit a gri file.  You may optionally customize gri-mode by:

 1. using the Custom interface (see the Help or Gri-Help menu or run the command M-x gri-customize), or

 2. manually setting variables in your ~/.emacs file.  These are briefly described by typing C-h m while in gri-mode.  Then, for further infomation, use emacs' describe-variable command, bound to C-h v.  For example, for more information about the gri*WWW-program variable, you'd type C-h v gri*WWW-program (note that emacs does Tab completion, so pressing the Tab key after typing-in gri will display all gri related variables.)

Major Gri-mode commands.
========================

This section describes the major gri-mode commands, briefly showing how they can increase your productivity.

How gri-mode names Gri commands
-------------------------------

A major feature of Gri mode is the completion of partially typed commands.  Let's examine how gri-mode decides to name gri commands.  A name is determined by removing bracketed options from the syntax line of a given command.  This is different from what the gri parser does.  In this way, the gri command

     draw label "\string" [centered|rightjustified] at .x. .y. [cm] [rotated .deg.]

is named by gri-mode simply draw label at.  Note how the `at' stays in the name because it is not optional.  So when you see draw label at in gri-mode's menus or prompts, you are more likely to associate the name with what the command actually does.

Possible completions of gri command names
-----------------------------------------

When you press M-tab to complete a command name (or a variable or synonym name as described below), gri-mode will expand it as much as it can and do nothing further.  If you type in nothing more and insist by using gri-complete (M-tab) again, gri-mode will respond by showing all possible completions in the *completions* buffer.  In this way you can use gri-complete word-by-word to abbreviate commands without ever displaying completions, like you would for file completion in emacs or bash.

If a completion is ambiguous, but could be exact, invoke gri-complete a second time to complete it. e.g.

     shM-tab

expands to

     show

and informs you that 12 possible completions exists; then

     showM-tab

will display these completions in the completions buffer; then typing M-tab again forces completion to a complete but not unique possibility:

     show .value.|{rpn ...}|"\text" [.value.|{rpn ...}|text [...]]

Completions are shown immediately (without invoking gri-complete again) if the completions window is already displayed or if there are 3 possibilities or less.  In this case they are displayed in the minibuffer.

Note: The *completions* window is deleted after a command is fully completed.  gri-complete uses its own *completions* buffer, which is not displayed in the buffer-list to avoid clutter.

Command name abbreviation
-------------------------

gri-mode uses command name abbreviations in a non-Unix way in that all words that compose the command name may be abbreviated (and not only the word preceding the cursor).  For example, one can type in

     dr x aM-tab

and it will expand1 all the words to

     draw x axis [at bottom|top|{.y. [cm]} [lower|upper]]

This is reminiscent of VMS, which the author was used to when gri-mode.el was initially created.  It's likely that a gri-mode.el rewritten from scratch wouldn't have this feature since it's not part of the Unix mindset.

Variable (and synonym) completion
---------------------------------

It's also possible to do M-tab completion on gri builtin variable and synonym names while editing a command.  Simply type in the leading . (dot) or \ (slash) character and invoke completion with M-tab.

For example,

     ..xM-tab

displays a completions buffer listing the possible completions:

     ..xmargin..                        ..xsize..
     ..xleft..                          ..xright..
     ..xlast..

Typing in an extra m will complete to ..xmargin.. and the following help information will be displayed in the minibuffer:

     margin to left of axis area. Default is 6 cm.

Editing the syntax output by gri-complete
-----------------------------------------

You might wonder what to do with all the bracketed code left behind by gri-complete.  It certainly won't go through the gri parser without error, so you have to edit it out.

The tools provided in gri-mode are gri-option-select (C-C C-o) and gri-kill-option (C-C C-k) to narrow in on a particular gri command, given a syntax description left on the line by gri-complete.  The cursor location is used to decide which gri command(s) to narrow to.

For example, if gri-complete is used on the line `dr x a', the result will be a line like

     draw x axis [at bottom|top|{.y. [cm]} [lower|upper]]

This is the gri way of describing many commands at once.  The above syntax description is a shortcut formulation for all of:

     draw x axis
     draw x axis at bottom
     draw x axis at bottom top
     draw x axis at bottom bottom
     draw x axis at top
     draw x axis at top top
     draw x axis at top bottom
     draw x axis at .y. cm
     draw x axis at .y. cm lower
     draw x axis at .y. cm upper

The gri-option-select (C-C C-o) command provides easy navigation to select one of these commands.  The narrowing process is governed by the cursor position.  For example, to get the command narrowed down to

     draw x axis at bottom [lower|upper]

place the cursor somewhere in the word `bottom' and invoke gri-option-select.  To complete the narrowing process, selecting

     draw x axis at bottom lower

move the cursor to some place in the word `lower' and invoke gri-option-select again.  On the other hand, to get

     draw x axis at bottom

you would have put the cursor over either the word `lower' or `upper', and invoke gri-kill-option (C-C C-k) instead.

You might want to practice using this example to learn how to do it.  If you make a mistake, note that the normal Emacs undo works.

User commands with gri-mode
---------------------------

User gri commands defined in ~/.grirc (Resource File) or at the beginning of a gri file can also be used with gri-complete. Note that user commands are added from the current buffer whenever `gri-mode' is invoked.  They may override previous user commands, but not gri system commands.

Inserting gri code fragments in Emacs
-------------------------------------

Since gri version 1.063, gri has special commands that begin with a question mark `?'.  These special commands have no options, and are composed only of standard gri commands.  Their purpose is to provide a short-cut for entering many lines of gri at once (e.g. bits of sample code about contouring grids, or your own preamble which you use at the time to set fonts and line widths).

gri-complete acts in a special way with these commands, by replacing the abbreviated name which you are completing by all the lines contained within the gri command.

The user is allowed to define new fragments in ~/.grirc, and also to override the gri system fragments.  You can therefore fine-tune gri's fragments to your taste.  To see the names of all gri fragments, type in a question mark at the beginning of a line in a gri buffer and press M-Tab twice to gri-complete it and display possible choices.  The gri commands used to replace them are found in the *gri-syntax* buffer.

Info interface for help on current command
------------------------------------------

The Info system is built into Emacs (C-h i), and provides an easy method of navigation on-line help (including this manual).  We suggest that you install the gri info files on your system (they are already installed with packaged versions of gri in Debian or Red Hat formats).

Not only will Info (C-h i) be able to navigate through all of gri's inline manual, but gri-mode's function gri-info-this-command (C-c C-i) will display the correct info page about the gri command being edited on the current line.

Additionally, gri-mode has the command gri-info (C-c M-i) which will prompt you (using tab completion) for any command to list Info about.  There's also a menu-bar pull-down menu which lists all gri commands, and you can get to Info from that too.

Other features of gri-mode
==========================

  * IMenu support: IMenu is a GNU/Emacs package used to source code files.  It can be setup for a particular mode to list a menu of function definitions and variable declarations.  In gri-mode, the IMenu is available from the menubar and provides links to new command declarations as well as value settings for variables and synomyns.

  * Toolbar support: XEmacs21 and Emacs-21 have support for a toolbar (a set of iconic buttons that are shortcuts for commands), however the two editors don't not have compatible toolbar setups.  Currently gri-mode only defines a single icon for XEmacs (to run gri on the current buffer) and defines three for GNU/Emacs (to run gri, to view the postscript file, and to lookup Info about the command on the current line).

  * Idle Help: When GNU/Emacs sits idle with the cursor on a command line, it looks up any defaults the command may have and displays the information in the minibuffer.  For example, sitting on a line that says set font size 10, it will display set font size: default is 12 point in variable ..fontsize...

Dealing with many Gri versions, gri-mode handles it.
====================================================

Earlier we explained that you might have many versions of gri installed on your system (Installing gri-mode.el).  You may use gri-mode to access these various versions with the following gri-mode commands:

  * gri-set-version: Tells gri-mode to use a given version as the default for all your gri files.  Tab completion is available listing all available versions (if they are not all listed, that means that the Emacs variable gri*directory-tree is not correctly set (Installing gri-mode.el)).  Your selection is stored in the file ~/.gri-using-version and is remembered across editing sessions. If you select default as your answer, gri-mode reverts to using the default version of gri as installed on your system (which may change after you update it) and deletes the ~/.gri-using-version file.

  * gri-set-local-version: Tells gri-mode to use a given version of gri this gri file (the one currently being edited when you invoke the command).  Tab completion is again available to list all available versions.  Your selection overrides the default version selected by gri-set-version for this file, and is stored as an Emacs variable at the bottom of the gri file.  It is remembered across editing sessions. If you select default as your answer, gri-mode reverts to using the default version of gri as selected by gri-set-version and deletes the Emacs variable setting at the bottom of the gri file.

Filename arguments when running gri
===================================

Usually, gri is run specifying only a gri command file to process, which lends itself well to the gri-mode command gri-run.  But Gri can be also invoked from the command line using optional arguments, usually filenames but not necessarily, e.g.

     $ gri somefile.gri datafile.dat datafile2.dat ...

or

     $ gri somefile.gri *.dat

The arguments are accessed with RPN operators argc and argv (Unary Operators).

gri-mode provides a method to set the arguments (usually filenames) to use when gri-run is called in a specific gri script.  Use the gri-mode command gri-set-command-postarguments to setup a string that gri-mode will use, and the gri-mode command gri-unset-command-postarguments to clear it.  For ease-of-use, these commands are made available from the menubar under the Perform -> Run Settings entries.  The specified string will be stored in the locally-defined (aka buffer-local) variable gri-command-postarguments and will be written within a gri comment at the bottom of the file such that Emacs remembers it across editing sessions.

History of Gri Versions
***********************

Gri, like many modern software projects, has two ``streams'' of development running side by side.  One is called ``stable,'' the other ``unstable.''  Most users should use the stable stream, which has been well tested.  (The unstable version is for users who wish to try out new features that are under development.)

Stable versions always have an even number as the middle number in their version designation, e.g. 2.6.0, while unstable versions always have an odd number there, e.g. 2.7.0.  This middle number indicates a sort of family of related releases.  Within a stable stream, all versions sharing a given middle number have the same features; new releases are made only to fix bugs.  Thus, version 2.6.1 fixed bugs in version 2.6.0.

To learn more about the bugs, and their resolution, visit the bugs page at gri.sourceforge.net (http://sourceforge.net/tracker/?func=browse&group_id=5511&atid=105511) and adjust the "status" menu to read "closed".

Stable Stream
=============

In any given stable stream, only the version with a 0 as the last number in the triplet has new features; the later versions only correct flaws.  For example, version 2.6.0 offers new features compared to any of the 2.4.x versions, but 2.6.1 differs only in the fixing of bugs.

Version 2.12
------------

Version 2.12.23 [2011 July 6 Malawai Independence Day (http://en.wikipedia.org/wiki/Malawi)]
............................................................................................

Bug fixes

  * https://sourceforge.net/projects/gri/forums/forum/16975/topic/4596628/index/page/1 ... pgm images grayscale was wrong

Version 2.12.22
...............

Bug fixes

  * Fix github bug http://github.com/dankelley/gri/issues#issue/5 ... draw image failed on some black/white images

Version 2.12.21 [2010 June 8 World Ocean Day (http://en.wikipedia.org/wiki/World_Oceans_Day)]
.............................................................................................

Bug Fixes

  * Fix github bug http://github.com/dankelley/gri/issues#issue/1 ... convert grid to image directly misplaced image ``patches'' by one patch width and one patch height

Version 2.12.20 [2010 April 9 Vimy Ridge Day (http://en.wikipedia.org/wiki/Vimy_Ridge_Day)]
...........................................................................................

New Features

  * add labelling option to set x axis and set y axis.

  * add directly option to convert grid to image.

Bug Fixes

  * Fix SourceForge bug #2913919 (https://sourceforge.net/forum/forum.php?thread_id=2913919&forum_id=16974) ... SVG: all symbols are "."

  * Fix SourceForge bug #2913893 (https://sourceforge.net/forum/forum.php?thread_id=2913893&forum_id=16974) ... svg segfault on draw label

  * Fix SourceForge bug #2913841 (https://sourceforge.net/forum/forum.php?thread_id=2913841&forum_id=16974) ... svg draw box filled not filled

  * Fix SourceForge bug #2913840 (https://sourceforge.net/forum/forum.php?thread_id=2913840&forum_id=16974) ... svg images are upside-down

  * Fix SourceForge bug #2913838 (https://sourceforge.net/forum/forum.php?thread_id=2913838&forum_id=16974) ... image postscript clip problem

Version 2.12.19 [2009 July 17 World Day for International Justice (http://en.wikipedia.org/wiki/World_Day_for_International_Justice)]
.....................................................................................................................................

New Features

  * Fix SourceForge ``bug'' #2977816 (https://sourceforge.net/forum/forum.php?thread_id=2977816&forum_id=16974) ... Fedora packaging requires more precise license declarations.

Bug Fixes

  * Fix SourceForge bug #3266884 (https://sourceforge.net/forum/forum.php?thread_id=3266884&forum_id=16974) ... error in docs for strlen.

Version 2.12.18 [2008 Sep 8 International Literacy Day (http://en.wikipedia.org/wiki/International_Literacy_Day)]
.................................................................................................................

Bug Fixes

  * Improve security of temporary-file handling.

  * Fix SourceForge bug #1985862 (http://sourceforge.net/tracker/index.php?func=detail&aid=1985862&group_id=5511&atid=105511) ... SVG output had axis linewidth equal to curve line width.

Version 2.12.17 [2008 May 29 Oak Apple Day (England) (http://en.wikipedia.org/wiki/Oak_Apple_Day)]
..................................................................................................

New Features

  * Add GNU readline support so that interactive mode will have history, command editing, etc.

Bug Fixes

  * Fix SourceForge bug #1913577 (https://sourceforge.net/tracker/?func=detail&atid=105511&aid=1913577&group_id=5511) ... superscripts did not end correctly, if preceeded by an inline {} block.

  * Fix SourceForge bug #1761562 (https://sourceforge.net/tracker/index.php?func=detail&aid=1761562&group_id=5511&atid=105511) ... y axis name printed upside down, for log axes in which user specified a high values at the bottom end of the axis

Version 2.12.16 [2007 Jul 20 anniversary of the first moon landing (http://en.wikipedia.org/wiki/Apollo_11)]
............................................................................................................

Bug Fixes

  * Fix Debian bug #130802 (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=130802) ... postscript problem in landscape mode, refreshed in gv viewer

  * Fix Debian bug #434010 (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=434010) ... set page landscape requires set page size first, but it should really default to something reasonable instead.

Version 2.12.15 [2007 Apr 16 celebration of birthday of Muhammad (http://en.wikipedia.org/wiki/Mawlid)]
.......................................................................................................

Bug Fixes

  * Fix SourceForge bug #1700978 (https://sourceforge.net/tracker/index.php?func=detail&aid=1700978&group_id=5511&atid=105511) ... html concept index mostly broken

  * Fix SourceForge bug #1698924 (https://sourceforge.net/tracker/index.php?func=detail&aid=1698924&group_id=5511&atid=105511) ... box plots show missing data

  * Fix Debian bug #417217 ... will not compile in GCC 4.3

  * Fix SourceForge bug #1698116 (https://sourceforge.net/tracker/index.php?func=detail&aid=1698116&group_id=5511&atid=105511) ... poorly-positioned name of RHS y-axis

Version 2.12.14 [2007 Jan 08: Coming-of-Age Day (Japan) (http://en.wikipedia.org/wiki/Seijin_shiki)]
....................................................................................................

Bug Fixes

  * Fix SourceForge bug #1630768 (https://sourceforge.net/tracker/index.php?func=detail&aid=1630768&group_id=5511&atid=105511) ... Fix to segfault in clipped images (a bug that may have developed after version 2.13.3)

Version 2.12.13 [2006 Nov 06: Constitution Day (Tajikistan) (http://en.wikipedia.org/wiki/Public_holidays_in_Tajikistan)]
.........................................................................................................................

Bug Fixes

  * Fix SourceForge bug #1591475 (https://sourceforge.net/tracker/index.php?func=detail&aid=1591475&group_id=5511&atid=105511) ... Fix to compile in Solaris CC

  * Fix SourceForge bug #1591062 (https://sourceforge.net/tracker/index.php?func=detail&aid=1591062&group_id=5511&atid=105511) ... Fix to compile in OpenBSD

Version 2.12.12 [2006 July 16: Yellow Pigs Day (http://en.wikipedia.org/wiki/Yellow_Pig%27s_Day)]
.................................................................................................

Bug Fixes

  * Fix SourceForge bug #1523033 (https://sourceforge.net/tracker/index.php?func=detail&aid=1523033&group_id=5511&atid=105511) ... Malloc error (freeing something already freed?)

  * Fix SourceForge bug #1523032 (https://sourceforge.net/tracker/index.php?func=detail&aid=1523032&group_id=5511&atid=105511) ... create columns from function bug, if there is an existing directory called tmp.

  * Fix SourceForge bug #1491105 (https://sourceforge.net/tracker/index.php?func=detail&aid=1491105&group_id=5511&atid=105511) ... set x axis labels had no affect for log axes (same for y)

Version 2.12.11 [2006 Mar 30: Hindu New Year]
.............................................

Bug Fixes

  * Fix SourceForge bug #1449546 (https://sourceforge.net/tracker/index.php?func=detail&aid=1449546&group_id=5511&atid=105511) ... x axis limits not correctly inferred from set x grid (same for y).

Version 2.12.10 [2006 Jan 26: Australia Day]
............................................

Bug Fixes

  * Fix SourceForge bug #1408259 (https://sourceforge.net/tracker/?func=detail&atid=105511&aid=1408259&group_id=5511) ... PostScript file contained private information.  This was fixed by adding new commandline arguments -private and -no_private, the former of which (the new default) means to not include the user's name, the invocation arguments, or the command-file contents (Invoking Gri).

  * Fix SourceForge bug #1285180 (http://sourceforge.net/tracker/index.php?func=detail&aid=12851803&group_id=5511&atid=105511) ... NaN was mishandled.  (The bug may have arisen in version 2.12.7 or thereabouts.)

  * Port to the FreeBSD (http://www.freebsd.org/) operating system, with help from Christopher Illies and Roman Neuhauser.

  * Fix SourceForge bug #1217273 (http://sourceforge.net/tracker/index.php?func=detail&aid=1217273&group_id=5511&atid=105511) ... missing some version numbers within docs

  * Fix SourceForge bug #1196613 (http://sourceforge.net/tracker/index.php?func=detail&aid=1196613&group_id=5511&atid=105511) ... user-supplied x-axis labels can run offscale (fix for y-axis later...)

  * Fix SourceForge bug #1198341 (http://sourceforge.net/tracker/index.php?func=detail&aid=1198341&group_id=5511&atid=105511) ... x-axis labels incorrectly rotated (sometimes)

  * Fix SourceForge bug #1199280 (http://sourceforge.net/tracker/index.php?func=detail&aid=1199280&group_id=5511&atid=105511) ... warning about malloc for RPN assignments

  * Fix SourceForge bug #1196115 (http://sourceforge.net/tracker/index.php?func=detail&aid=1196115&group_id=5511&atid=105511) ... gri_unpage and gri_merge mis-installed

  * Fix SourceForge bug #1153209 (http://sourceforge.net/tracker/index.php?func=detail&aid=1153209&group_id=5511&atid=105511) ... Emacs mode incompatible with new version of gv PostScript viewer

     Fix SourceForge bug #1101172 (http://sourceforge.net/tracker/index.php?func=detail&aid=1101172&group_id=5511&atid=105511) ... gri -help incorrectly stated meaning of last argument(s)

  * Fix SourceForge bug #835711 (http://sourceforge.net/tracker/index.php?func=detail&aid=835711&group_id=5511&atid=105511) ... draw gri logo fails.

  * Fix SourceForge bug #1098269 (http://sourceforge.net/tracker/index.php?func=detail&aid=1098269&group_id=5511&atid=105511) ... problem compiling on AMD64 machine.  (Solution provided by Andreas Jochens, a Debian user.)

  * Fix SourceForge bug #867515 (http://sourceforge.net/tracker/index.php?func=detail&aid=867515&group_id=5511&atid=105511) ... problem with junk appearing in images.

  * Fix SourceForge bug #875881 (http://sourceforge.net/tracker/index.php?func=detail&aid=875881&group_id=5511&atid=105511) ... problem compiling with gcc 2.95.3 compiler.

Version 2.12.9 [2005 Jan 6: Feast of Epiphany (http://en.wikipedia.org/wiki/Epiphany_%28feast%29)]
..................................................................................................

Bug Fixes

  * Fix SourceForge bug #1094087 (http://sourceforge.net/tracker/index.php?func=detail&aid=1094087&group_id=5511&atid=105511) ... set path to incorrectly parsed colon-separated paths

  * Fix SourceForge bug #1085788 (http://sourceforge.net/tracker/index.php?func=detail&aid=1085788&group_id=5511&atid=105511) ... image *=, image /=, image ^=, and image _= all gave incorrect results

  * Fix SourceForge bug #1084123 (http://sourceforge.net/tracker/index.php?func=detail&aid=1084123&group_id=5511&atid=105511) ... does not compile in fink

  * Fix SourceForge bug #676767 (http://sourceforge.net/tracker/index.php?func=detail&aid=676767&group_id=5511&atid=105511) ... on fink systems, help does not work

Version 2.12.8 [2004]
.....................

Bug Fixes

  * Fix SourceForge bug #1019141 (http://sourceforge.net/tracker/index.php?func=detail&aid=1019141&group_id=5511&atid=105511) ... draw arc ignores the present pen color

  * Fix SourceForge bug #997741 (http://sourceforge.net/tracker/index.php?func=detail&aid=997741&group_id=5511&atid=105511) ... PostScript broken on images with y-axis decreasing, and enclosed by PostScript clipping

  * Fix SourceForge bug #978822 (http://sourceforge.net/tracker/index.php?func=detail&aid=978822&group_id=5511&atid=105511) ... documentation wrong on set path to

  * Fix SourceForge bug #932203 (http://sourceforge.net/tracker/index.php?func=detail&aid=932203&group_id=5511&atid=105511) ... misplaced labels caused by set x axis labels

  * Fix SourceForge bug #928277 (http://sourceforge.net/tracker/index.php?func=detail&aid=928277&group_id=5511&atid=105511) ... draw polygon should take cm and pt units

  * Fix SourceForge bug #930259 (http://sourceforge.net/tracker/index.php?func=detail&aid=930259&group_id=5511&atid=105511) ... fix draw arc's drawing of an extra line (thanks for the fix, Wolfgang Voegeli)

  * Fix SourceForge bug #923719 (http://sourceforge.net/tracker/index.php?func=detail&aid=923719&group_id=5511&atid=105511) ... draw curve overlying ignored the effect of set dash

  * Fix SourceForge bug #914125 (http://sourceforge.net/tracker/index.php?func=detail&aid=914125&group_id=5511&atid=105511) ... offpage points in axes were reported as having been drawn by draw curve.

  * Fix SourceForge bug #877613 (http://sourceforge.net/tracker/index.php?func=detail&aid=877613&group_id=5511&atid=105511) ... help (and other commands using temporary files) does not work in OSX/Fink version.

  * Fix SourceForge bug #874483 (http://sourceforge.net/tracker/index.php?func=detail&aid=874483&group_id=5511&atid=105511) ... state save doesn't keep track of dash settings.

  * Fix SourceForge bug #873245 (http://sourceforge.net/tracker/index.php?func=detail&aid=873245&group_id=5511&atid=105511) ... inaccurate times are given in the warnings about slow operations on OSX platform (days are reported instead of seconds)

  * Fix SourceForge bug #871477 (http://sourceforge.net/tracker/index.php?func=detail&aid=871477&group_id=5511&atid=105511) ... the `missing value' feature should not be the default.  The solution involved adding a new command set missing value none, which is now the default.

Version 2.12.7 [2003 Sep 4]
...........................

Bug Fixes

  * Fix SourceForge bug #800022 (http://sourceforge.net/tracker/index.php?func=detail&aid=800022&group_id=5511&atid=105511) AKA Debian bug #208589 (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=208589), ... did not build on some Debian platforms because it was based on an old version of automake.

Version 2.12.6 [2003 Sep 1: Labour Day]
.......................................

New Features

  * Add age RPN function, for testing file ages (age-rpn-operator).

Bug Fixes

  * Fix SourceForge bug #773850 (http://sourceforge.net/tracker/index.php?func=detail&aid=773850&group_id=5511&atid=105511) ... bounding-box is increased by draw symbol even if (rectangular) postscript clipping is active.

  * Fix SourceForge bug #760130 (http://sourceforge.net/tracker/index.php?func=detail&aid=760130&group_id=5511&atid=105511) ... Solaris cannot compile with C-l in Makefile.

  * Fix SourceForge bug #743134 (http://sourceforge.net/tracker/index.php?func=detail&aid=743134&group_id=5511&atid=105511) ... bounding box not limited by set clip postscript

  * Fix SourceForge bug #750561 (http://sourceforge.net/tracker/index.php?func=detail&aid=750561&group_id=5511&atid=105511) ... during compilation, make rebuilds HTML docs even if up-to-date

Version 2.12.5 [2003 May 19: Victoria Day]
..........................................

New Features

  * Apply a patch provided Kawamura Masao, relating to (a) errors in the documentation of file locations and (b) a programming error hidden behind an unset precompiler flag.

  * Add hexadecimal colornames (pen-color-hexadecimal).

Bug Fixes

  * Fix SourceForge bug #739761 (http://sourceforge.net/tracker/index.php?func=detail&aid=739761&group_id=5511&atid=105511) ... draw time stamp named the command-file incorrectly

  * Fix SourceForge bug #720607 (http://sourceforge.net/tracker/index.php?func=detail&aid=720607&group_id=5511&atid=105511) ... the emacs mode looked for html documentation files in an incorrect location on linux/redhat systems

Version 2.12.4 [2003 Apr 06]
............................

Bug Fixes

  * Fix SourceForge bug #696073 (http://sourceforge.net/tracker/index.php?func=detail&aid=696073&group_id=5511&atid=105511) ... did not handle \$() syntax correctly.

  * Fix SourceForge bug #715884 (http://sourceforge.net/tracker/index.php?func=detail&aid=715884&group_id=5511&atid=105511) ... mixup on protected-quotes within double-quoted strings

  * Fix Debian bug #183912 (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=183912) ... would not compile on m86k architecture.

  * Fix SourceForge bug #711354 (http://sourceforge.net/tracker/index.php?func=detail&aid=711354&group_id=5511&atid=105511) ... Creator: comment in PostScript file named the command-file incorrectly, if there were options on the gri invocation command.  Since this naming of the command-file was not especially useful, and since nobody has complained of this bug but the author, the feature has simply been deleted.  Just complain if you want it back!

  * Fix SourceForge bug #706202 (http://sourceforge.net/tracker/index.php?func=detail&aid=706202&group_id=5511&atid=105511) ... A hint about the page orientation was not given in the Postscript comments.  The lack of this hint has no affect on printing, etc., only viewing in some viewers.

Version 2.12.3 [2003 Mar 1]
...........................

Bug Fixes

  * Fix SourceForge bug #685919 (http://sourceforge.net/tracker/index.php?func=detail&aid=685919&group_id=5511&atid=105511) ... -output commandline argument failed on .eps file extension.

Version 2.12.2 [2003 Feb 7: Munro Day at Dalhousie University (http://www.dal.ca/)]
...................................................................................

Bug Fixes

  * Fix SourceForge bug #675304 (http://sourceforge.net/tracker/index.php?func=detail&aid=675304&group_id=5511&atid=105511) ... Segmentation fault can occur on read image pgm if an image already exists, e.g. created by convert grid to image.

  * Fix SourceForge bug #647234 (http://sourceforge.net/tracker/index.php?func=detail&aid=647234&group_id=5511&atid=105511) ... Source file draw.cc will not compile on MAC OS X 10.1.5 at optimization level 2, so drop the level to no optimization, as a temporary measure.

  * Fix SourceForge bug #671022 (http://sourceforge.net/tracker/index.php?func=detail&aid=671022&group_id=5511&atid=105511) ... flip image x|y did not flip images correctly, except in special circumstances.

  * Fix SourceForge bug #669603 (http://sourceforge.net/tracker/index.php?func=detail&aid=669603&group_id=5511&atid=105511) ... skip backward .n. erroneously skipped forward

  * Fix SourceForge bug #667754 (http://sourceforge.net/tracker/index.php?func=detail&aid=667754&group_id=5511&atid=105511) ... read image pgm segfaults on memory if an image has already been created by convert grid to image

  * Fix SourceForge bug #664388 (http://sourceforge.net/tracker/index.php?func=detail&aid=664388&group_id=5511&atid=105511) ... read image pgm fails if an image already exists

  * Fix SourceForge bug #654129 (http://sourceforge.net/tracker/index.php?func=detail&aid=654129&group_id=5511&atid=105511) ... ignoring ~/.grirc file

  * Fix SourceForge bug #654127 (http://sourceforge.net/tracker/index.php?func=detail&aid=654127&group_id=5511&atid=105511) ... configure scripts are broken

  * Fix SourceForge bug #649132 (http://sourceforge.net/tracker/index.php?func=detail&aid=649132&group_id=5511&atid=105511) ... removed unused LDFLAGS phrase from Makefile

  * Fix SourceForge bug #649134 (http://sourceforge.net/tracker/index.php?func=detail&aid=649134&group_id=5511&atid=105511) ... tweak gcc optimization

  * Fix SourceForge bug #649136 (http://sourceforge.net/tracker/index.php?func=detail&aid=649136&group_id=5511&atid=105511) ... examples 8 and 9 broken

  * Fix SourceForge bug #641406 (http://sourceforge.net/tracker/index.php?func=detail&aid=641406&group_id=5511&atid=105511) ... RPN too aggressive on missing values

Version 2.12.1 [2002 Sep 25]
............................

Bug Fixes

  * Fix SourceForge bug #613075 (http://sourceforge.net/tracker/index.php?func=detail&aid=613075&group_id=5511&atid=105511) ... RPN operators sin, cos, and tan were limited in range (new bug in last release)

Version 2.12.0 [2002 Sep 15: Terry Fox Day (http://www.terryfox.org/), Canada.]
...............................................................................

New Features

  * Add sed RPN operator, to work on strings Binary Operators.

  * Add skewness and kurtosis RPN operators, to work on columns Manipulation of Columns etc.

Removed Features

  * n/a

Bug Fixes

  * Fix SourceForge bug #606303 (http://sourceforge.net/tracker/index.php?func=detail&aid=606303&group_id=5511&atid=105511) ... web-pages were not valid html-4.0.

  * Fix SourceForge bug #593958 (http://sourceforge.net/tracker/index.php?func=detail&aid=593958&group_id=5511&atid=105511) ... missing-values should be ignored if they occur in intermediate results of RPN calculations.

  * Fix SourceForge bug #600395 (http://sourceforge.net/tracker/index.php?func=detail&aid=600395&group_id=5511&atid=105511) ... won't compile with recently released version (3.2) of GCC compiler.

  * Fix SourceForge bug #600233 (http://sourceforge.net/tracker/index.php?func=detail&aid=600223&group_id=5511&atid=105511) ... segfaults if some RPN operators are used on stacks that do not contain enough entries (e.g. show {rpn cosh}).

Version 2.10
------------

Version 2.10.1 [2002 Jun 1]
...........................

Bug Fixes

  * Fix SourceForge bug #562911 (http://sourceforge.net/tracker/index.php?func=detail&aid=562911&group_id=5511&atid=105511) ... won't build with gcc-3.0 compiler.  This was reported by the Debian hppa builder as Debian bug #148572 (http://bugs.debian.org/148572).

  * Fix SourceForge bug #562558 (http://sourceforge.net/tracker/index.php?func=detail&aid=562558&group_id=5511&atid=105511) ... draw title terminates program if have non-positive data and had initially specified log axes.

  * Fix SourceForge bug #562014 (http://sourceforge.net/tracker/index.php?func=detail&aid=562014&group_id=5511&atid=105511) ... won't build if popt library is unavailable.  This was reported by the Debian ia64 builder as Debian bug #148493 (http://bugs.debian.org/148493).

  * Fix SourceForge bug #558463 (http://sourceforge.net/tracker/index.php?func=detail&aid=558463&group_id=5511&atid=105511) ... in HTML docs, the ``press'' margin tag was misdirected.

  * Fix SourceForge bug #562017 (http://sourceforge.net/tracker/index.php?func=detail&aid=562017&group_id=5511&atid=105511) ... parser fails with DOS end-of-line.

  * Fix SourceForge bug #562113 (http://sourceforge.net/tracker/index.php?func=detail&aid=562113&group_id=5511&atid=105511) ... new page postscript error in gv viewer.

Version 2.10.0 [2002 May 20: Victoria Day]
..........................................

New Features

  * In the documentation, change the names of some variables to be clearer: ll_x is now written xleft, etc.

  * Add RPN binary operators and, or for logical operations Binary Operators, along with negation operator not Unary Operators.

  * Add draw arc command (Draw Arc).

  * Add set x axis labels (Set X Axis) and set y axis labels (Set Y Axis) commands.

  * Permit specification of pt units for draw label (Draw Label), draw box (Draw Box), draw symbol at (Draw Symbol At), and draw line from (Draw Line From).

  * Add set clip to curve (Set Clip) command. Caution: this needs extension, and may have a bug if called twice in succession [but is this with an intervening set clip off]

  * Add group and end group commands, in preparation for SVG output.  So far these commands do nothing, and are basically just a signal that users should not create commands with these names since Gri will need them soon.

  * Add ..xinc.. and ..yinc.. builtin variables (Axis Scaling).

  * Make the open command accept URLs as filenames (Open).

Removed Features

  * Remove gri -repair old.ps new.ps since (a) it was only half functional, (b) it was hard to code in the new scheme of argument-processing and (c) the author was not aware of anybody every having used it.

  * Make the -chatty commandline option require a value (Invoking Gri).

Bug Fixes

  * Fix SourceForge bug #552009 (rpn can segfault if != operator is written as =!)

  * Fix SourceForge bug #546109 (bounding box wrong if postscript clipping used)

  * Fix SourceForge bug #514495 in which set clip to curve failed to handle missing values in the curve.

  * Fix SourceForge bug #450465 (create columns from function was broken).

Version 2.8
-----------

Version 2.8.7 [2002 Apr 03]
...........................

  * Fix SourceForge bug #482120 (regress ignores data weights)

  * Fix SourceForge bug #508657 (missing backslash in drawing undefined synonyms)

  * Fix SourceForge bug #523450 (log axes detect non-positive values too late)

  * Fix SourceForge bug #521045 (installation/compilation with Solaris Workshop V6 Update 2 compiler)

Version 2.8.6 [2002 Feb 14]
...........................

  * Fix SourceForge bug #513002 (minor documentation error in set clip)

  * Fix SourceForge bug #509592 (HTML docs had midordered indices)

  * Fix SourceForge bug #506534 (map axes give wrong minutes in negative regions).  Thanks, Brian, for the patch on this!

  * Fix SourceForge bug #508088 (grimode: gv should update, not be relaunched)

  * Fix SourceForge bug #506490 (-v commandline option returned wrong version number)

Version 2.8.5 [2001 Dec 13]
...........................

  * Fix SourceForge bug #492472 (inf rpn operator caused segfault)

Version 2.8.4 [2001 Oct 4]
--------------------------

  * Fix SourceForge bug #467973 (gri -version gave wrong version number, breaking the Emacs Gri mode.)

  * Fix SourceForge bug #468014 (draw grid disobeyed pencolor.)

Version 2.8.3 [2001 Oct 1]
..........................

  * Fix SourceForge bug #462243 (endian problem in Rasterfile images + reading problem in PGM images).

Version 2.8.2 [2001 Sep 19]
...........................

  * Fix SourceForge bug #461444 (wouldn't compile with the mingw32 compiler, for windows 32 machines).

  * Fix SourceForge bug #454557 (wouldn't compile with the pre-release version 3.0.1 of the GNU c++ compiler, in the case in which netCDF was already installed)

Version 2.8.1 [2001 Sep 7]
..........................

  * Fix SourceForge bug #450465 (create columns from function was broken).

  * Fix SourceForge bug #454557 (wouldn't compile with the pre-release version 3.0.1 of the GNU c++ compiler)

Version 2.8.0 [2001 Jul 30]
---------------------------

New command syntax

  * Add unlink command as a unix-familiar way to delete files (Unlink).

  * Add set page size command to clip to a given page size (Set Page).

  * Add substr RPN operator to permit extraction of sub-strings (Tertiary Operators).

  * Add default possibility for the set x name and the set y name commands.

  * Add Perl-like ability to put underscores in numerical constants, to guide your eye.  These underscores are ignored by Gri, so that for example .v. = 1_000 and .v. = 1000 are equivalent as far as Gri is concerned.

Emacs mode (Emacs Mode)

  * Give M-Tab the ability to complete builtin variables and synonyms as well as commands

  * Add ``idle-timer minibuffer help'' to display defaults for builtin variables under the cursor.

  * Add fontification of builtin variables only if they are spelled correctly.

Developer changes

  * Add make source-arch-indep target in sources.  This will build a source tar file in which all the architecture-independent material (documentation in HTML, postscript and Info formats) is pre-made.  This makes it easier to install gri on a host that doesn't have TeX and ImageMagick installed.

  * Complete the port to IBM's compiler for their AIX operating system.

Version 2.6
-----------

Version 2.6.4 [2001 Jul 9: Dan's birthday]
------------------------------------------

  * Fix SourceForge bug #435688 (remnants of polar column type, no longer supported, remained in documentation)

  * Fix SourceForge bug #435603 (set dash produced broken PostScript)

  * Fix SourceForge bug #431114 (-0 could appear on axes)

Version 2.6.3 [2001 Jun 22]
---------------------------

  * Fix SourceForge bug #433250 (draw symbol ignored dashing state sometimes)

  * Fix SourceForge bug #432549 (contours sometimes unlabelled)

  * Tweak internal coding for compilation on AIX compilers.

Version 2.6.2 [2001 May 19]
...........................

  * Fix SourceForge bug #425174 (synonym interpolation broken on e.g. show "[\syn]"

  * Fix SourceForge bug #425175 (while !..eof.. acted ignored end of file)

Version 2.6.1 [2001 May 10]
...........................

  * Fix SourceForge bug #420499 (gri-mode.el compatibility issues with emacs-21;  Mostly bad old code.)

  * Fix SourceForge bug #421076 (byte-compiled gri-mode.el has broken IMenu support;  Affects Debian package.)

  * Fix SourceForge bug #419599 (wouldn't compile under GNU g++ 3.x compiler)

  * Fix SourceForge bug #418065 (documentation mentions back-tic notation, which is not available)

  * Fix SourceForge bug #417333 (vague error message RPN string operator)

  * Fix SourceForge bug #415277 (make fails on MSDOS)

  * Fix SourceForge bug #415149 (file.cc parse error on MSDOS)

  * Fix SourceForge bug #414520 (draw symbol ... at should automatically produces axes unless the location is in cm coordinates)

  * Fix SourceForge bug #414010 (items in the html concept index were in an odd order)

  * Fix SourceForge bug #413986 (~username was broken in open)

  * Fix SourceForge bug #411904 (/ was ugly in math mode)

Version 2.6.0 [2001 April 1]
............................

  * Permit rewind to take a filename.

  * Make open set \.return_value. to the full pathname of the file that was opened.

  * Add set path command (Set Path To).

  * Remove functioning of GRIINPUTS environment variable, since this is more cleanly handled with the newly added set path to command (Set Path To).

  * Remove \.awk. synonym, which was deemed to be unhelpful.  Users with many scripts that use this variable might wish to put a line like

          \.awk. = "gawk"

     in their ~/.grirc file.

  * Change the format of images in the PostScript output file, as a workaround for a bug in the ps2pdf program.

  * Add ``ampersand'' (\& and \&&) syntax to permit newcommands to look up the name and nesting level of changeable arguments (Changeable Command Arguments).

  * Add ``at-sign'' (@) syntax for aliases (Alias Synonyms).

  * Add ability to embed newlines in show commands with the \<< sequence (Show).

  * Add ability to embed TAB characters in show commands with the \>> sequence (Show).

  * Make various read commands (Read) able to decode synonyms as well as variables and simple numbers.

  * Add strlen RPN operator (Unary Operators).

  * Add default option to set x format and set y format commands.

  * Add new postscript file (New Postscript File) command.

  * Switch email list from majordomo to GNU mailman.

  * No longer remove comments from data lines that are read.  This served little function, interfered with recent user code, and could be accomplished by reading through a sed pipe in any case.

  * Make the first element of the argv array be the name of the command-file.  (This makes Gri consistent with languages such as C.)

  * Add chapter on test suite (Test Suite).

  * Let newcommands have changeable arguments (Changeable Command Arguments).

  * Remove -s as an abbreviation for the commandline option -superuser.

  * Remove the : syntax from the commandline options.

  * Add commandline option -output PS_file_name.

  * Add assert command (Assert).

  * Add test suite (mainly for developers).

  * Add sleep command (Sleep).

  * Remove command show hint of the day, since I no longer permission to use cgi-bin to provide the hints via web-server.

  * Permit indexing of synonym words with variables, in addition to constants.

  * Fix bug in interpolating synonyms in the test-expression of while loops.

  * Put source on the Source Forge open-source development website, at http://gri.sourceforge.net. Gri users can benefit from this site in may ways.  First, it is a great way to keep track of new versions.  With a mouse-click you can cause SourceForge to email you whenever a new version of Gri is released. Second, SourceForge has newsgroups (http://sourceforge.net/forum/?group_id=5511) and email lists (http://sourceforge.net/mail/?group_id=5511) devoted to Gri.  These are archived, so that you can stop monitoring them for a while and then go back and see what you've missed.  Third, Source Forge has a powerful bug-tracking facility. (http://sourceforge.net/bugs/?group_id=5511) With this you may check for existing bugs reported by users, submit new bug reports, and also track the process of bug removal (e.g. optionally receiving emails when the bug is removed).

  * Add set colorname command (Set Colorname).

  * Add source command (Source).

  * Add RPN operators wordc (Solitary Operators) and wordv (Unary Operators) for accessing the words in the present Gri command.

  * Add RPN operators argc (Solitary Operators) and argv (Unary Operators) for accessing the command-line arguments used when Gri was invoked from the operating system.

  * Add automatic support for compressed data files.  So far, this only works with gzipped files (Open).

  * Add two new RPN operators, file_exists and directory_exists (Unary Operators).

  * Reorganize parts of manual (e.g.  changing the section about the Emacs gri-mode.el into a chapter, with screen snapshots).

  * Improve the HTML form of the manual (e.g. color-code the Gri syntax in examples, provide access to all the indices, use Jpeg format, et.).

  * Add several new features to gri-mode.el:

     1) Add a menubar pull-down menu listing all Gri commands, allowing the user to get Help or Info on any command or Insert it in the current Gri file.

     2) Add a menubar pull-down entry to Perform to set gri-run settings such as flag options passed to gri.

     3) Gri info file can have .info extension now.

     4) Made gri-apropos an alias for gri-help-apropos.

     5) gri-mode now uses the customize interface (See gri-customize).

     6) The ~/.gri-syntax file has changed format.  As a side-effect, spaces are used instead of hyphens to display Gri commands, and one can now select a command with the mouse in the Completions buffer.

Version 2.4
-----------

Version 2.4.4 [2000 May 7]
..........................

Change so that only a warning is printed if mathematical operations are requested on empty arrays (e.g. y += 10).  Previously, an error was reported and Gri exited with an error condition, which is bothersome in scripts that rely on successful completion of the Gri job.

Port to the BeOS operating system.

Version 2.4.3 [2000 Apr 1]
..........................

Change location of all files, to be consistent with Redhat convention. Previously, things were in /opt/gri; now they are in more standard locations.

Version 2.4.2 [2000 Mar 25]
...........................

Remove bug in which convert grid to image produced incorrect images, visible as a patchy appearance with coarse grids.

Version 2.4.1 [2000Jan 31]
..........................

Remove bug in which convert image to grid failed to take note of the gri minimum and maximum, so that contouring of the grid was not possible for grids created from images.

Version 2.4.0 [2000 Jan 05]
...........................

Add set input data separator.  Make read columns work with various input separators. Make read .x., etc, work with various input separators.

Version 2.2
-----------

Version 2.2.6 [1999 Nov 25]
...........................

Make web-based manual easier to read by putting a light-grey background under sample code.

Version 2.2.5 [1999 Nov 10]
...........................

Fix bug in RPN calculations that prevented using a negative exponent.

Version 2.2.4 [1999 Nov 7]
..........................

Add set font encoding, and also change the encoding to ISO-Latin-1.  (This doesn't hurt old code since Gri didn't make any claims to handle characters outside the normal printing-set before anyway.)

Fix bug in which there were 4 dead links in the HTML version of manual.

Clean up some problems with Debian distribution (thanks, Peter Galbraith!).

Version 2.2.3 [1999 Jun 30]
...........................

Fix bug in which word-of-synonym (e.g. \[0]mysyn) was not detected correctly (thanks to bug report from Kazuhiko Nakayama in Japan)

Version 2.2.2 [-]
.................

Clean a few spelling and cross-reference errors in documentation.

Version 2.2.1 [1999 Mar 31]
...........................

For debian, properly locate the netcdf library, if it is installed.

Remove remnants of old commands for polar axes.

Correct error in which the right-most and upper-most pixel of images created by convert grid to image may be blank (or not, depending on roundoff error) under certain conditions of exact matchup between grid spacing and image spacing.

Don't create PostScript file if the commandfile is non-existent, or if there were errors on the commandline.

Version 2.2.0 [1999 Mar 25]
...........................

First debian release.  Versions exist for intel, alpha, 68K and powerpc.

Unstable Stream
===============

Development Version
-------------------

The list below shows changes that have been made in the development version of Gri, i.e. the version on CVS at http://gri.sourceforge.net.  Some or all of these features may enter the next stable stream of Gri, but it is important to note that anything that's listed here may be changed without notice!  The main exception is bug fixes, which will enter the stable stream unless they are found to create new bugs.

New Features
............

  * n/a

Removed Features
................

  * n/a

Bug Fixes
.........

  * Fix SourceForge bug #618041 (http://sourceforge.net/tracker/index.php?func=detail&aid=618041&group_id=5511&atid=105511) ... solaris compile error, relating to the subroutine gethostname() in the startup.cc source code file.

Plans
-----

Some plans for future versions are given below.  A more extensive list, together with target timescales and notes on the progress towards completion, is available in the to-do list at the development site (http://gri.sourceforge.net), which is also the place to go if you have suggestions for other changes to Gri.

High Priority
.............

 1. Add ability to generate SVG (scalable vector graphics) output.  This file type can be edited with GUI-based tools, making it easy for users to put the final touches on graphs "manually."  This feature will require a great deal of work, mainly to do with grouping of graphical elements, and so I'll need to rely on advice from users.

 2. Switch to popt library for the processing of command-line options.  (Docs on this are at http://cvs.gnome.org/lxr/source/popt.)

 3. Change set axes style from number-based selection to word-based selection, and print a deprecation warning if the number-based syntax is used.

 4. Switch from tmpname to mkstemp subroutine, for temporary filenames.

 5. Add readline support, to handle history, command-line editing, etc, for interactive usage (Docs on this are at http://cnswww.cns.cwru.edu/~chet/readline/readline.html.)

Medium priority
...............

 1. Add optimal interpolation as another method for gridding data (Convert Columns To Grid).

 2. Add ability to read PNG images (Read Image) (Docs on this are at http://www.libpng.org/pub/png/.)

Low priority
............

 1. Add non-RPN mathematics.

 2. Add graphical output to the screen as commands are executed.

 3. Add support for both little-endian and big-endian binary data.

Deprecated Commands
===================

  * version 2.9.0

       * Replace set y axis label horizontal with set y axis name horizontal.

       * Replace set y axis label vertical with set y axis name vertical.

Installing Gri
**************

Unix Installation
=================

Archiving Old Versions
======================

Gri, like other complex programs, sometimes changes in such a way as to break old scripts.  This is less so of changes since about 1998 or so, since the syntax became pretty firm about that time.

Still, disk costs are so cheap that you would be well-advised to keep a backup version of Gri, whenever you update.  This is pretty simple; you need to keep a copy of the executable and the library file, and you need to write a tiny shellscript that calls this particular executable with this particular library file.  For example, you might do the following

     mkdir -m 755 -p           /usr/local/share/gri/2.12.23
     cp /usr/bin/gri           /usr/local/share/gri/2.12.23
     cp /usr/share/gri/gri.cmd /usr/local/share/gri/2.12.23

and then create a shellscript called /usr/local/bin/gri-2.12.23 containing

     #!/usr/bin/sh
     /usr/local/share/gri/2.12.23/gri \
         -directory /usr/local/share/gri/2.12.23 \
         "$@"

to invoke this version of Gri.

To be able to access this old version of gri from within the Emacs gri-mode, you would reset the Emacs variable gri*directory-tree like so in the file ~/.emacs (Step 2 in Installing gri-mode.el)

     (setq gri*directory-tree
         '("/usr/local/share/gri/" "/usr/share/gri/"))

Installation on Linux computers
-------------------------------

Installation is easy on various flavors of linux.  Versions are available from the official distributions and also at http://sourceforge.net/project/showfiles.php?group_id=5511

The RedHat version supports intel platforms only, while the Debian version supports intel, alpha, 68K and powerpc.  Installation follows the normal method for these distributions ... if you have the distribution, you surely know what to do.  If you don't, you may want to switch when you see that you can install Gri by clicking an icon in a window, or by typing, e.g. in RedHat linux:

     rpm -i gri-2.12.23

Debian-linux installation may be done with any of several GUI-based tools, or with the following system command:

     dkpg -i gri_2.12.23-1_i386.deb

or via a properly configured apt interface that will fetch the latest version from the net:

     apt-get install gri

Pre-compiled unix versions
--------------------------

Pre-compiled versions of Gri exist for various computers, e.g. SPARC (both sunOS and solaris), IBM-RS, Sequent, and Linux.  The following instructions, which assume a version number 2.12.23, and a SPARC solaris machine, show how to install these.

The compressed tar file, with a name like gri-binary-SunOS5-2.12.23.tar.gz (in this example a Sun OS 5 binary is assumed, with gri version number 2.12.23) contains a directory which holds the executable Gri file, gri, the library file gri.cmd, an instructions file, README, and a Makefile to install Gri.

Here's how to install Gri, starting with this tar file:

 1. First, uncompress (unzip) the file, and un-tar it, by doing

          gunzip -c gri-binary-SunOS5-2.12.23.tar.gz | tar xvf -

     or

          zcat gri-binary-SunOS5-2.12.23.tar.gz | tar xvf -

     This will yield a new directory, with a name like gri-binary-SunOS5-2.12.23, which contains the indicated files.

 2. Follow the instructions in the README file to install Gri.

Compilation on Unix computers
=============================

The following steps indicate how to compile Gri on unix computers.  The procedure is quite standard.

Requirements
     You'll need a C++ compiler that is modern enough to handle 'templates' (i.e. almost any compiler from 1998 onward).  Don't worry -- if your compiler isn't new enough, you'll see that in a minute or two!

     You'll need TeX and texinfo to make the info files, and optionally the netCDF library (if you wish gri to be able to read netCDF binary data files).  To make the HTML manual, you'll need imagemagick, info, gs and its fonts.

     On Debian GNU/Linux systems, the required packages are listed as Build-Depends in the control file found in the debian directory, to which you must add the package build-essential.

Unpack the source
     Type

          gunzip gri-2.12.23.tgz
          tar xvf gri-2.12.23.tar

     (or similar commands) to uncompress and untar the contents.  This will yield a new directory named gri-2.12.23 which contains many files.

Move to the Gri directory

          cd gri-2.12.23

Configure your compiler
     Next you must "configure" the Gri source files.  During this step, a series of tests will be made about your operating system and your compiler.  Most of these tests need no interaction from you, but there is one overall choice that you may wish to make: the place on your filesystem where Gri (and many associated library and documentation files) will reside.  To get the default installation, with files residing within the directory /usr/local, type

          ./configure

     at this time.  If you'd rather the files go into another location, run the configure script differently, e.g.  to get the Gri files to reside within the /opt directory, type:

          ./configure --prefix=/opt

     In response, you'll see the results of several tests of the properties of your operating system, your C++ compiler, etc.  Normally you can ignore these results.

     As an example, typing ./configure without a --prefix option yields the directory tree (... indicates several files not displayed in this list, for brevity).  In this example, the most up-to-date version is 2.12.23, but a previous version 2.12.22 has also been retained.  (Note that only one copy of the documentation is retained; this is all that's needed, since old versions are documented there as well as new versions.)

          /usr/local
          |-- bin
          |   |-- gri -> gri-2.12.23
          |   |-- gri-2.12.23
          |   |-- gri-2.12.22
          |   |-- gri_merge
          |   `-- gri_unpage
          |-- info
          |   |-- ...
          `-- share
              `-- gri
                  |-- 2.6.0
                  |   |-- gri.cmd
                  |   |-- license.txt
                  |   |-- logo.dat
                  |   `-- startup.msg
                  |-- 2.4.0
                  |   |-- gri.cmd
                  |   |-- license.txt
                  |   |-- logo.dat
                  |   `-- startup.msg
                  `-- doc
                      |-- examples
                      |   |-- ...
                      `-- html
                          |-- ...
                          |-- resources
                          |   |-- ...
                          `-- screenshots
                              |-- ...

     Trouble-shooting 1: If the permission of the configure file is wrong, you'll get an error like Permission denied; if so, try typing sh ./configure to run it in the Bourne shell.  If that fails, you are going to have to do some old-fashioned work!  Start by copying the generic Makefile called Makefile.generic into Makefile, and try the following steps, perhaps editing the Makefile if you run into errors.

     Trouble-shooting 2: Gri uses a C++ feature called 'templates'. Unfortunately, templates are handled in different ways by different compilers.  At least as of Spring 1997, the GNU compiler, vsn 2.7.x (used by many Gri folks) has problems with templates.  Therefore the configure script will check to see if you are using the GNU c++ compiler, and if you are it will check whether the ("template repository") compiler flag -frepo is known on your machine.  If it is not, an alternative method of templates will be used.  But if it is, you'll be asked, for confirmation, whether you wish to use the -frepo flag.  On many machines (e.g. Solaris) you should answer n to this question.  The prompt will explain.  Also, note that you can avoid the prompt by running configure as either of the two below:

          ./configure --enable-frepo
          ./configure --disable-frepo

     (Such switches will be ignored unless you're using the GNU compiler.)

     Trouble-shooting 3: If optional system libraries like the netCDF library, if it exists, are installed in nonstandard places, you might have to change the unix environment variable LD_LIBRARY_PATH. For example, on my machine the netcdf library is not installed in /usr/lib, as the configure script assumes, but rather in /usr/local/share/netcdf/lib.  Therefore I have the following line in one of my startup files:

          export LD_LIBRARY_PATH=/usr/lib:/usr/local/share/netcdf/lib

Compiling Gri
     Now compile Gri by typing

          make

Testing Gri
     Type

          make check

     to do some tests on the version of Gri that you just compiled.  If no errors are reported, you may go to the next step.

Installing Gri
     Assuming compilation succeeds, install gri and the ancillary file gri.cmd, by typing

          make install

     If you wish to see where files where be installed, first try a dry run typing

          make -n install

Cleaning up
     Once these things are done, you may type

          make clean
          cd doc ; make clean

     to clean up some files.  Of course, you could just erase the whole source, but the source is probably worth a penny of hard-drive space, isn't it?

Compilation on x86 (PC-style) Computers
=======================================

Versions exist for MSDOS, windows, and Linux operating systems. (Actually, the windows version is just the MSDOS version, which can be run inside an msdos window within windows-95, windows-NT, etc.)

MSDOS Operating System
----------------------

To compile and install Gri under MSDOS, do this:

 1. To begin, install DJGPP V2, if it is not on your system already. It can be found at http://www.delorie.com/djgpp

 2. Uncompress and extract from gri source package (Uncompiled Unix).

 3. Type make -f Makefile.dj2 to compile.  If it fails, you might have to edit the file Makefile.dj2 to match the characteristics of your system.  Please inform the author, Dan Kelley at Dan.Kelley@Dal.CA, if you think your modifications might be useful to others.

 4. Type make -f Makefile.dj2 install to install it (normally on the C: drive).

If you encounter problems, read the first few lines of the Makefile (i.e. the file Makefile.dj2) for hints on things to try.  For example, in the present version of Makefile.dj2 these hints are given:

 1. There is a good chance that this Makefile will work as is, so try that first.

 2. If you have the netcdf library (used for certain types of atmospheric and oceanographic datasets), then un-comment and possibly edit the appropriate NETCDF_... lines below, as instructed by the comments preceding these lines.

 3. If you don't want Gri inserted in the directory c:/gri, edit the instdir = ... line below.

 4. If you get error messages about the stdcxx library, edit the LIBS line below, rewriting -lstdcxx as -lstdcx.

 5. If you get compilation errors relating to time or to ftime, try putting the token -DHAVE_FTIME=1 in the list of similar token in the DEFS = ... line.  For consistency (basically, so the author can help you if you do this), put it right after the -D_GRI_=1 token.

To view the output, use a PostScript viewer such as GSview.

LINUX Operating System
----------------------

Linux is a good emulation of unix, and it is free.  Gri for linux is compiled and installed according to the normal unix instructions. The compiled version is with a name like gri-binary-solaris-2.1.10.tar.gz; treat it as in other unix systems (Uncompiled Unix).

Compilation under OS/2
======================

Gri compiles, using the gcc compiler under OS/2, provided that the included Makefile.os2 is used.  Be sure to edit the first few lines to change filenames as required, especially taking care to account for whether the netCDF library is installed, etc.

Compilation in Macintosh OS X
=============================

The OS X system provides a BSD unix that suites Gri very well. With the (free) developer package, it also provides a very up-to-date version of the gcc compiler. Thus, installing Gri on Macintosh can be done using the normal Unix instructions.

But there are also easier ways. Gri is compatible with Fink and Darwinports, the two popular packaging systems on OS X. If you use OS X and do not have Fink or Darwinports installed, then you should probably install one, or both. Each distribution has strengths, and each has weaknesses, and it is difficult to provide a firm recommendation between the two.

Caveat. As of mid-2007, neither distribution appears to handle package dependencies as well as is done by popular linux distributions. For example, in working through the steps listed below, the author found that his Darwinports system had a problem with a system library that handles internationalization. The "update" operation of the system was insufficient to solve the problem, and so it was necessary to do some web searching to find a patch. The patch failed, but another search revealed a second (hand-edit) patch that got it working. In excess 4 CPU hours were required to rebuild the packages that were broken.

If you'd like to build a local Darwinports version of Gri, to get the latest version instead of whatever version is provided by Darwinports, follow these steps:

  * Download the source from CVS at SourceForge. (If you don't know what the previous sentence means, you will quite likely have difficulties with the other steps.)

  * Visit the darwinports directory of the newly-created directory tree, and type

          sudo port -d -v build

     to build it. This will take several minutes, during which you may find it helpful to do a search on "darwinport build". For example, the O'Reilly page (http://www.oreillynet.com/pub/a/mac/2004/04/09/darwinports.html?page=3, last checked in July 2007) is very good.  Note that you will be building from the source that is stored on SourceForge, not from the Darwinports source. That's the trick of issuing the build version of the port command.

  * Do a "destroot" operation:

          sudo port -d -v destroot

  * Install it:

          sudo port -d -v install

     Note: if you already have an older version of Gri in the Darwinports system, you must first issue the command

          sudo port deactivate gri

Compilation under BeOS
======================

The BeOS system compiles Gri cleanly without modification; just follow the instructions for unix.

Bugs
****

Known bugs
==========

To get a list of known bugs, in the present or past versions, visit http://sourceforge.net/tracker/?atid=105511&group_id=5511&func=browse.

Reporting Bugs
==============

Bug reports help make Gri more reliable and useful for all users, so please report any bugs you find.  The scheme will be familiar to you, if you've participated in open-source work before.

 1. Visit the bug-tracking part of the Source Forge Gri development site, at http://sourceforge.net/bugs/?group_id=5511 to see whether your bug has already been reported.  You may find that it has been reported and fixed already in a new version, in which case you should archive your existing Gri version and upgrade.  If the bug has been reported and not fixed, then you may still wish to add a supplemental bug report, so the author knows that this bug is of concern to you as well as the others.  (Plus, reporting it this way ensures that you'll receive an email when the bug is fixed.)

 2. Debugging is made easier if the problem is reduced in scope. Therefore, please reduce your application and your data to the simplest case that produces the error.

 3. If you know how, please try to find the bug yourself.  After all, Gri is open-source for a reason!  The procedure is described in the next section (Killing Bugs).

Killing Bugs
============

Software that you'll need
-------------------------

This section is intended to help you find and kill bugs yourself, by indicating how the author does this work.  Since Gri is open-source, all users are invited to try to kill bugs themselves!

If you know nothing of C or C++, you may as well not read further, since there is little chance of your making progress.  On the other hand, experienced programmers won't need any of the advice I give below.

You'll need the Gri source and a C++ compiler.  It also helps if you have gdb, the GNU debugger, installed; the instructions below assume that's the case.  Also, the instructions assume that you're using the Emacs editor, and running gdb from within Emacs. Otherwise, you'll want to glance at the documentation on gdb to see how to use it in standalone mode.

Debugging at a glance
---------------------

The list below is a sketch of what you might try, and in what order.

  * Check the bug list to see if other users have found your bug, and also to see if there is a workaround.

  * Try a more recent version of gri.  If it works, you might wish to archive the version you have at the moment and upgrade.

  * If you suspect your bug has something to do with system calls, as in the system command (System) or as in piped input files (Open), you should re-run the script with gri -superuser8 instead of with gri.  This will cause Gri to print out all commands that it is handing over to the operating system; you may see the error that way.  (Hint: it may help to interactively cut/paste the commands into your OS shell to see what the action of the command is.)

  * If your bug results in early termination, you should run Gri inside a debugger (e.g. GDB, assumed henceforth).  When the program terminates, type where to see where termination occured.  Often this will give a clue.  In many cases, early termination results from faults in memory allocation.  To check memory allocation, you'll need to recompile Gri, linking it against a debugging memory allocator.  Many such tools exist; see comments in the Makefile for a hint at how to use a popular one, called ``Electric Fence.''

  * If your bug does not result in early termination, you may find the best scheme is to trim your example down as much as possible, and then run Gri inside the GDB (or other debugger) so that you can monitor program execution.  The next section explains this in detail.

A debugging Example
-------------------

Let's take a recent bug as an example.  Peter Galbraith found that the gri script

     set color hsb 0.999 1 1
     draw box filled 2 2 3 3 cm
     set color hsb 1.000 1 1
     draw box filled 4 2 5 3 cm

produced odd results in a previous version of Gri; the color patches should have been of nearly the same color, but the first one was red, as expected, and the second was magenta.

The list below shows how I found Peter's bug.  Experienced C or C++ programmers will find all of this very familiar, and will really only need to read item 6 of the list below, since that's the only action that is really specific to Gri.  (Note: for display purposes, I've broken some of the lines in the files into two lines in this list.)

 1. Copy the above script (called test.gri) into the Gri source directory, and the script into an Emacs buffer.  Note: all the following steps are done within Emacs, and the items in parentheses are the Emacs keys to get the indicated actions.

 2. If you're working from a pre-compiled version, you'll need to get the source first and do a compile yourself (Uncompiled Unix).  Then do a make tags command (type this to the unix shell) to create a so-called "tag" table.

 3. Run Gri in this emacs buffer (C-cC-r) noting from the postscript window that pops up that the colors are, indeed, mixed up.

 4. Load up the gdb debugger by typing M-x gdb gri.  This will open a new Emacs buffer in which you may type commands.  We'll be switching back and forth between this buffer and various source files.

 5. Reasoning that the error probably occurs at set color or draw box, try replacing the latter by a command such as draw label "hi" at 3 3 cm".  The color is still wrong, indicating that it is the set color command that has the problem.

 6. Next, we must find where the C++ code corresponding to the set color command resides.  As it turns out, all set commands are defined in the source file set.cc, and this command is defined in a subroutine called set_colorCmd().  But the author knows this -- how would you?  The answer is to look in the gri.cmd file, for the set color command.  (Search for the string `set color .) Then read down to see the body of the command, enclosed in braces; you'll see

          {
              extern "C" bool set_colorCmd(void);
          }

     which indicates that the subroutine name is set_colorCmd().

 7. Next we need to edit this subroutine to see what it is doing. There are several ways to find it (e.g. grep through the source files), but the easiest is to use the "tags" feature of Emacs, by typing M-. set_colorCmd.  This will bring you to the indicated subroutine.

 8. Have a look through this subroutine to see what it is doing.  It looks very much like many other Gri subroutines.  A check is done on the number of words provided to the command, in the

          	switch (_nword) {

     line.  (That's line set.cc:484 at the moment -- but it may be different by the time you read this file, if I've changed it!)  We are calling it with 6 words (set color hsb 1.000 1 1), so move down to the line

          	case 6:

     and you'll see that there is an if statement seeing whether this word is rgb or hsv.  These statements are checking _word[2], which is the third word of the command.  (In Gri, as in C, words start at zero.  Thus, for this command, _word[0] is set, _word[1] is color, and _word[2] is expected to be either rgb or hsb.  We are having problems with the hsb style, so we'll move down to that code.  The code that's being executed is as follows.

          } else if (!strcmp(_word[2], "hsb")) {
                  // `set color hsb .hue. .saturation. .brightness.'
                  double          hue, saturation, brightness;
                  Require(getdnum(_word[3], &hue),
                          READ_WORD_ERROR(".hue."));
                  Require(getdnum(_word[4], &saturation),
                          READ_WORD_ERROR(".saturation."));
                  Require(getdnum(_word[5], &brightness),
                          READ_WORD_ERROR(".brightness."));
                  // Clip if necessary
                  CHECK_HSB_RANGE(hue);
                  CHECK_HSB_RANGE(saturation);
                  CHECK_HSB_RANGE(brightness);
                  gr_hsv2rgb(hue, saturation, brightness,
                          &red, &green, &blue);
                  PUT_VAR("..red..", red);
                  PUT_VAR("..green..", green);
                  PUT_VAR("..blue..", blue);
                  c.setHSV(hue, saturation, brightness);
                  _griState.set_color_line(c);
                  if (_griState.separate_text_color() == false)
                          _griState.set_color_text(c);
                  return true;

     The Require lines are ensuring that we could decode the values of the variables hue, etc, from the commandline.  Then we clip the range of these values.  Then we convert from hsb color format to rgb color format, save the values of the colors in Gri variables with PUT_VAR, and then set the color with c.setHSV. Finally we save this color in the Gri "state" with _griState.set_color_line(c).

     As it turns out, Gri outputs all colors to the PostScript file in RGB format, so the we may well suspect that the problem is in the gr_hsv2rgb() line.

 9. We have an idea where to look now, so let's go to the line just after it, in the editor, and insert a "breakpoint" there by typing C-x SPC.  Then move to the gdb buffer and re-run Gri by typing

          run -directory . test.gri

     to run Gri on our script.  Then, magic happens!  Gri stops at the indicated breakpoint, and Emacs will display both the gdb buffer and the set.cc buffer.  The latter has a margin indication telling what line were are on.  You may now type gdb commands in the gdb buffer.  In particular, type

          p hue

     to print the hue.  Then type

          p red

     to see the red value.  Then type

          c

     to continue running Gri.  It will pause again.  Check the hue and red values again, as above.  If you like, play around with hue value in the Gri script test.gri and run gri again (type r in gdb).  This seems to indicate that the conversion is working strangely.

 10. To see how the conversion is done, clear the breakpoints by typing delete in the gdb buffer, then insert a breakpoint before gr_hsv2rgb is called.  Then, run Gri again (r in the gdb buffer).  When it stops just before this subroutine, type s to "step into" the subroutine.  Then you'll see a conversion code from the (wonderful) textbook of Foley and Van Dam. You'll see

          void
          gr_hsv2rgb(double h, double s, double v,
                     double *r, double *g, double *b)
          {
          	h = 6.0 * pin0_1(h);
          	s = pin0_1(s);
          	v = pin0_1(v);
          	int i = (int) floor(h);
          	if (i > 5)
          		i = 5; // Prevent problem if hue is exactly 1
          	double f = h - i;
          	double p = v * (1.0 - s);
                  ...

     in the present version of Gri, but in the previous (buggy) version, the if statement was missing.  Without this if statement, Gri produced wrong colors.  With the statement, the colors are correct.

And so ends the example.  You may wish to read the Foley and Van Dam textbook to see just what I'm doing in gr_hsv2rgb, but suffice it to say that the problem in the (older) version of Gri was that i could take the value 6 if the hue was exactly equal to 1, and that was erroneous.

In reading the code, you may notice that it is formatted in a uniform way: the Kernighan and Ritchie scheme (from their classic C textbook), with 8-character indents.  I get this by putting the following lines in the ~/.emacs file, which is used to customize the Emacs editor:

     (defun my-c-mode-common-hook ()
       (c-set-style "K&R")
       (setq c-basic-offset 8)
       )
     (add-hook 'c-mode-common-hook 'my-c-mode-common-hook)

If you submit patches, please use the same format as I've done, so that I can more easily see the changes you've made.

Test Suite
**********

The following test files are invoked by typing make test, after compiling Gri.  They are provided here because they are examples of scripts that are known to work for the version of Gri described in this manual.

Heavy use is made of the assert command (Assert) in these test files.  Thus the code itself demonstrates the features, instead of comments in the code.  This is advantageous since comments tend to be incorrect!

Gri in the Press
****************

A gentle introduction to Gri is provided in a Linux Journal article, available at http://www2.linuxjournal.com/lj-issues/issue75/3743.html on the web.

In March 2000, I emailed some Gri users to ask for the names of scientific journals in which they have published Gri-produced graphs. The list, which mainly arrived on Sunday in response to an email I sent Saturday (don't Gri users take a break?) is presented below, to indicate the range of Gri use in the press.

Journals in Oceanography, Atmospheric Science, Earth Science, etc.

  * Bulletin on Coastal Oceanography (in Japanese with English abstract)

  * Fisheries Oceanography

  * Deep-Sea Research

  * EOS, Transactions of the American Geophysical Union

  * Estuarine, Coastal and Shelf Science

  * Geophysical Research Letters

  * Journal of Atmospheric and Oceanic Technology

  * Journal of Geophysical Research

  * Journal of Marine Research

  * Journal of Plankton Research

  * Journal of Physical Oceanography

  * Journal of the Japan Scoiety for Marine Surveys and Technology (in Japanese with English abstract)

  * Limnology and Oceanography

  * Marine Biology

  * Marine Ecology Progress Series

  * Monthly Weather Review

  * Oceanography

  * Paleoceanography

  * Progress in Oceanography

  * Quaternary Research

  * Scientia Marina

  * South African Journal of Marine Science

  * Umi no Kenkyu (Japanese version for Journal of Oceanography, in Japanese with English abstract)

Journals in Physics, Chemistry, etc.

  * Applied Physics A

  * Journal of Fluid Mechanics

  * Journal of Physical Chemistry B

  * Physica D

  * Physics of Fluids

  * Physics A

  * Physics Letters B

  * Physical Review C

  * Physical Review Letters

  * Research on Chemical Intermediates

  * Theoretical Computational Fluid Dynamics

Other Journals

  * Nature

Books, Monographs, etc.

  * The Atlas of Hawai'i (University of Hawai'i Press)

  * Differential Equations with Applications to Biology (American Mathematical Society)

  * Ocean Drilling Program publications

Acknowledgments
***************

Over the years, many Gri users have been kind enough to help in its development. Some have done so by sending in bug reports, others by requesting features, others by submitting patches.  A few of their names are: Ivo Alxneit, Karin Bryan, Sara Bennett, Luke Blaikie, Dave Brickman, Steve Cayford, Clyde Clements, Andrew Collier, Pierre Flament, Peter Galbraith, Dave Hebert, David A. Holland, Christopher Illies, Cody Kirkpatrick, Thomas Larsen, Alejandro López-Valencia, Kawamura Masao, Steve Matheson, Brian May, Ed Nather, Roman Neuhauser, Carl Osterwisch, Richard Andrew Miles Outerbridge, Tim Powers, Jinyu Sheng, Toru Suzuki, Keith Thompson, David Trueman, Wolfgang Voegeli, Jeff Whitaker, and George White.

Prime among these is Peter Galbraith, who has been a close collaborator in Gri development and in my scientific work, for two (!) decades.

To all, thanks.

License
*******

Gri is distributed under the GPL public license, an Open Source license that provides certain rights and freedom to users, notably the access to source code and the right to modify it and/or redistribute it. The full text of the GPL license is given below.

     		    GNU GENERAL PUBLIC LICENSE
     		       Version 2, June 1991

      Copyright (C) 1989, 1991 Free Software
          Foundation, Inc.  59 Temple Place, Suite
          330, Boston, MA 02111-1307 USA

      Everyone is permitted to copy and distribute
      verbatim copies of this license document, but
      changing it is not allowed.

     			    Preamble

       The licenses for most software are designed to
     take away your freedom to share and change it.
     By contrast, the GNU General Public License is
     intended to guarantee your freedom to share and
     change free software--to make sure the software
     is free for all its users.  This General Public
     License applies to most of the Free Software
     Foundation's software and to any other program
     whose authors commit to using it.  (Some other
     Free Software Foundation software is covered by
     the GNU Library General Public License instead.)
     You can apply it to your programs, too.

       When we speak of free software, we are
     referring to freedom, not price.  Our General
     Public Licenses are designed to make sure that
     you have the freedom to distribute copies of free
     software (and charge for this service if you
     wish), that you receive source code or can get it
     if you want it, that you can change the software
     or use pieces of it in new free programs; and
     that you know you can do these things.

       To protect your rights, we need to make
     restrictions that forbid anyone to deny you these
     rights or to ask you to surrender the rights.
     These restrictions translate to certain
     responsibilities for you if you distribute copies
     of the software, or if you modify it.

       For example, if you distribute copies of such a
     program, whether gratis or for a fee, you must
     give the recipients all the rights that you have.
     You must make sure that they, too, receive or can
     get the source code.  And you must show them
     these terms so they know their rights.

       We protect your rights with two steps: (1)
     copyright the software, and (2) offer you this
     license which gives you legal permission to copy,
     distribute and/or modify the software.

       Also, for each author's protection and ours, we
     want to make certain that everyone understands
     that there is no warranty for this free software.
     If the software is modified by someone else and
     passed on, we want its recipients to know that
     what they have is not the original, so that any
     problems introduced by others will not reflect on
     the original authors' reputations.

       Finally, any free program is threatened
     constantly by software patents.  We wish to avoid
     the danger that redistributors of a free program
     will individually obtain patent licenses, in
     effect making the program proprietary.  To
     prevent this, we have made it clear that any
     patent must be licensed for everyone's free use
     or not licensed at all.

       The precise terms and conditions for copying,
     distribution and modification follow.

     		    GNU GENERAL PUBLIC LICENSE

        TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION
        AND MODIFICATION

       0. This License applies to any program or other
     work which contains a notice placed by the
     copyright holder saying it may be distributed
     under the terms of this General Public License.
     The "Program", below, refers to any such program
     or work, and a "work based on the Program" means
     either the Program or any derivative work under
     copyright law: that is to say, a work containing
     the Program or a portion of it, either verbatim
     or with modifications and/or translated into
     another language.  (Hereinafter, translation is
     included without limitation in the term
     "modification".)  Each licensee is addressed as
     "you".

     Activities other than copying, distribution and
     modification are not covered by this License;
     they are outside its scope.  The act of running
     the Program is not restricted, and the output
     from the Program is covered only if its contents
     constitute a work based on the Program
     (independent of having been made by running the
     Program).  Whether that is true depends on what
     the Program does.

       1. You may copy and distribute verbatim copies
     of the Program's source code as you receive it,
     in any medium, provided that you conspicuously
     and appropriately publish on each copy an
     appropriate copyright notice and disclaimer of
     warranty; keep intact all the notices that refer
     to this License and to the absence of any
     warranty; and give any other recipients of the
     Program a copy of this License along with the
     Program.

     You may charge a fee for the physical act of
     transferring a copy, and you may at your option
     offer warranty protection in exchange for a fee.

       2. You may modify your copy or copies of the
     Program or any portion of it, thus forming a work
     based on the Program, and copy and distribute
     such modifications or work under the terms of
     Section 1 above, provided that you also meet all
     of these conditions:

         a) You must cause the modified files to carry
         prominent notices stating that you changed
         the files and the date of any change.

         b) You must cause any work that you
         distribute or publish, that in whole or in
         part contains or is derived from the Program
         or any part thereof, to be licensed as a
         whole at no charge to all third parties under
         the terms of this License.

         c) If the modified program normally reads
         commands interactively when run, you must
         cause it, when started running for such
         interactive use in the most ordinary way, to
         print or display an announcement including an
         appropriate copyright notice and a notice
         that there is no warranty (or else, saying
         that you provide a warranty) and that users
         may redistribute the program under these
         conditions, and telling the user how to view
         a copy of this License.  (Exception: if the
         Program itself is interactive but does not
         normally print such an announcement, your
         work based on the Program is not required to
         print an announcement.)

     These requirements apply to the modified work as
     a whole.  If identifiable sections of that work
     are not derived from the Program, and can be
     reasonably considered independent and separate
     works in themselves, then this License, and its
     terms, do not apply to those sections when you
     distribute them as separate works.  But when you
     distribute the same sections as part of a whole
     which is a work based on the Program, the
     distribution of the whole must be on the terms of
     this License, whose permissions for other
     licensees extend to the entire whole, and thus to
     each and every part regardless of who wrote it.

     Thus, it is not the intent of this section to
     claim rights or contest your rights to work
     written entirely by you; rather, the intent is to
     exercise the right to control the distribution of
     derivative or collective works based on the
     Program.

     In addition, mere aggregation of another work not
     based on the Program with the Program (or with a
     work based on the Program) on a volume of a
     storage or distribution medium does not bring the
     other work under the scope of this License.

       3. You may copy and distribute the Program (or
     a work based on it, under Section 2) in object
     code or executable form under the terms of
     Sections 1 and 2 above provided that you also do
     one of the following:

         a) Accompany it with the complete
         corresponding machine-readable source code,
         which must be distributed under the terms of
         Sections 1 and 2 above on a medium
         customarily used for software interchange;
         or,

         b) Accompany it with a written offer, valid
         for at least three years, to give any third
         party, for a charge no more than your cost of
         physically performing source distribution, a
         complete machine-readable copy of the
         corresponding source code, to be distributed
         under the terms of Sections 1 and 2 above on
         a medium customarily used for software
         interchange; or,

         c) Accompany it with the information you
         received as to the offer to distribute
         corresponding source code.  (This alternative
         is allowed only for noncommercial
         distribution and only if you received the
         program in object code or executable form
         with such an offer, in accord with Subsection
         b above.)

     The source code for a work means the preferred
     form of the work for making modifications to it.
     For an executable work, complete source code
     means all the source code for all modules it
     contains, plus any associated interface
     definition files, plus the scripts used to
     control compilation and installation of the
     executable.  However, as a special exception, the
     source code distributed need not include anything
     that is normally distributed (in either source or
     binary form) with the major components (compiler,
     kernel, and so on) of the operating system on
     which the executable runs, unless that component
     itself accompanies the executable.

     If distribution of executable or object code is
     made by offering access to copy from a designated
     place, then offering equivalent access to copy
     the source code from the same place counts as
     distribution of the source code, even though
     third parties are not compelled to copy the
     source along with the object code.

       4. You may not copy, modify, sublicense, or
     distribute the Program except as expressly
     provided under this License.  Any attempt
     otherwise to copy, modify, sublicense or
     distribute the Program is void, and will
     automatically terminate your rights under this
     License.  However, parties who have received
     copies, or rights, from you under this License
     will not have their licenses terminated so long
     as such parties remain in full compliance.

       5. You are not required to accept this License,
     since you have not signed it.  However, nothing
     else grants you permission to modify or
     distribute the Program or its derivative works.
     These actions are prohibited by law if you do not
     accept this License.  Therefore, by modifying or
     distributing the Program (or any work based on
     the Program), you indicate your acceptance of
     this License to do so, and all its terms and
     conditions for copying, distributing or modifying
     the Program or works based on it.

       6. Each time you redistribute the Program (or
     any work based on the Program), the recipient
     automatically receives a license from the
     original licensor to copy, distribute or modify
     the Program subject to these terms and
     conditions.  You may not impose any further
     restrictions on the recipients' exercise of the
     rights granted herein.  You are not responsible
     for enforcing compliance by third parties to this
     License.

       7. If, as a consequence of a court judgment or
     allegation of patent infringement or for any
     other reason (not limited to patent issues),
     conditions are imposed on you (whether by court
     order, agreement or otherwise) that contradict
     the conditions of this License, they do not
     excuse you from the conditions of this License.
     If you cannot distribute so as to satisfy
     simultaneously your obligations under this
     License and any other pertinent obligations, then
     as a consequence you may not distribute the
     Program at all.  For example, if a patent license
     would not permit royalty-free redistribution of
     the Program by all those who receive copies
     directly or indirectly through you, then the only
     way you could satisfy both it and this License
     would be to refrain entirely from distribution of
     the Program.

     If any portion of this section is held invalid or
     unenforceable under any particular circumstance,
     the balance of the section is intended to apply
     and the section as a whole is intended to apply
     in other circumstances.

     It is not the purpose of this section to induce
     you to infringe any patents or other property
     right claims or to contest validity of any such
     claims; this section has the sole purpose of
     protecting the integrity of the free software
     distribution system, which is implemented by
     public license practices.  Many people have made
     generous contributions to the wide range of
     software distributed through that system in
     reliance on consistent application of that
     system; it is up to the author/donor to decide if
     he or she is willing to distribute software
     through any other system and a licensee cannot
     impose that choice.

     This section is intended to make thoroughly clear
     what is believed to be a consequence of the rest
     of this License.

       8. If the distribution and/or use of the
     Program is restricted in certain countries either
     by patents or by copyrighted interfaces, the
     original copyright holder who places the Program
     under this License may add an explicit
     geographical distribution limitation excluding
     those countries, so that distribution is
     permitted only in or among countries not thus
     excluded.  In such case, this License
     incorporates the limitation as if written in the
     body of this License.

       9. The Free Software Foundation may publish
     revised and/or new versions of the General Public
     License from time to time.  Such new versions
     will be similar in spirit to the present version,
     but may differ in detail to address new problems
     or concerns.

     Each version is given a distinguishing version
     number.  If the Program specifies a version
     number of this License which applies to it and
     "any later version", you have the option of
     following the terms and conditions either of that
     version or of any later version published by the
     Free Software Foundation.  If the Program does
     not specify a version number of this License, you
     may choose any version ever published by the Free
     Software Foundation.

       10. If you wish to incorporate parts of the
     Program into other free programs whose
     distribution conditions are different, write to
     the author to ask for permission.  For software
     which is copyrighted by the Free Software
     Foundation, write to the Free Software
     Foundation; we sometimes make exceptions for
     this.  Our decision will be guided by the two
     goals of preserving the free status of all
     derivatives of our free software and of promoting
     the sharing and reuse of software generally.

     			    NO WARRANTY

       11. BECAUSE THE PROGRAM IS LICENSED FREE OF
     CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO
     THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT
     WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
     HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM
     "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
     EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED
     TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
     FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE
     RISK AS TO THE QUALITY AND PERFORMANCE OF THE
     PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE
     DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY
     SERVICING, REPAIR OR CORRECTION.

       12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE
     LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT
     HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
     REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE
     LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL,
     SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
     ARISING OUT OF THE USE OR INABILITY TO USE THE
     PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
     DATA OR DATA BEING RENDERED INACCURATE OR LOSSES
     SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF
     THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
     EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
     ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

     		     END OF TERMS AND CONDITIONS

     	    How to Apply These Terms to Your New
     	    Programs

       If you develop a new program, and you want it
     to be of the greatest possible use to the public,
     the best way to achieve this is to make it free
     software which everyone can redistribute and
     change under these terms.

       To do so, attach the following notices to the
     program.  It is safest to attach them to the
     start of each source file to most effectively
     convey the exclusion of warranty; and each file
     should have at least the "copyright" line and a
     pointer to where the full notice is found.

         <one line to give the program's name and a
         brief idea of what it does.> Copyright (C)
         yyyy <name of author>

         This program is free software; you can
         redistribute it and/or modify it under the
         terms of the GNU General Public License as
         published by the Free Software Foundation;
         either version 2 of the License, or (at your
         option) any later version.

         This program is distributed in the hope that
         it will be useful, but WITHOUT ANY WARRANTY;
         without even the implied warranty of
         MERCHANTABILITY or FITNESS FOR A PARTICULAR
         PURPOSE.  See the GNU General Public License
         for more details.

         You should have received a copy of the GNU
         General Public License along with this
         program; if not, write to the Free Software
         Foundation, Inc., 59 Temple Place, Suite 330,
         Boston, MA 02111-1307 USA

     Also add information on how to contact you by
     electronic and paper mail.

     If the program is interactive, make it output a
     short notice like this when it starts in an
     interactive mode:

         Gnomovision version 69, Copyright (C) yyyy
         name of author Gnomovision comes with
         ABSOLUTELY NO WARRANTY; for details type
         `show w'.  This is free software, and you are
         welcome to redistribute it under certain
         conditions; type `show c' for details.

     The hypothetical commands `show w' and `show c'
     should show the appropriate parts of the General
     Public License.  Of course, the commands you use
     may be called something other than `show w' and
     `show c'; they could even be mouse-clicks or menu
     items--whatever suits your program.

     You should also get your employer (if you work as
     a programmer) or your school, if any, to sign a
     "copyright disclaimer" for the program, if
     necessary.  Here is a sample; alter the names:

       Yoyodyne, Inc., hereby disclaims all copyright
       interest in the program `Gnomovision' (which
       makes passes at compilers) written by James
       Hacker.

       <signature of Ty Coon>, 1 April 1989
       Ty Coon, President of Vice

     This General Public License does not permit
     incorporating your program into proprietary
     programs.  If your program is a subroutine
     library, you may consider it more useful to
     permit linking proprietary applications with the
     library.  If this is what you want to do, use the
     GNU Library General Public License instead of
     this License.