README
1NAME
2 Chart::Math::Axis - Implements an algorithm to find good values for
3 chart axis
4
5SYNOPSIS
6 # Create a new Axis
7 my $axis = Chart::Math::Axis->new;
8
9 # Provide is some data to calculate on
10 $axis->add_data( @dataset );
11
12 # Get the values for the axis
13 print "Top of axis: " . $axis->top . "\n";
14 print "Bottom of axis: " . $axis->bottom . "\n";
15 print "Tick interval: " . $axis->interval_size . "\n";
16 print "Number of ticks: " . $axis->ticks . "\n";
17
18 # Apply the axis directly to a GD::Graph.
19 $axis->apply_to( $graph );
20
21DESCRIPTION
22 Chart::Math::Axis implements in a generic way an algorithm for finding a
23 set of ideal values for an axis. That is, for any given set of data,
24 what should the top and bottom of the axis scale be, and what should the
25 interval between the ticks be.
26
27 The terms "top" and "bottom" are used throughout this module, as it's
28 primary use is for determining the Y axis. For calculating the X axis,
29 you should think of 'top' as 'right', and 'bottom' as 'left'.
30
31METHODS
32 new
33 my $null = Chart::Math::Axis->new;
34 my $full = Chart::Math::Axis->new( @dataset );
35
36 The "new" method creates a new "Chart::Math::Axis" object. Any arguments
37 passed to the constructor are used as dataset values. Whenever the
38 object has some values on which to work, it will calculate the axis. If
39 the object is created with no values, most methods will return undef.
40
41 max
42 Returns the maximum value in the dataset.
43
44 min
45 Returns the minimum value in the dataset.
46
47 top
48 The "top" method returns the value that should be the top of the axis.
49
50 bottom
51 The "bottom" method returns the value that should be the bottom of the
52 axis.
53
54 maximum_intervals
55 Although Chart::Math::Axis can work out scale and intervals, it doesn't
56 know how many pixels you might need, how big labels etc are, so it can
57 determine the tick density you are going to need. The
58 "maximum_intervals" method returns the current value for the maximum
59 number of ticks the object is allowed to have.
60
61 To change this value, see the "set_maximum_intervals" method. The
62 default for the maximum number of intervals is 10.
63
64 interval_size
65 The "interval_size" method returns the interval size in dataset terms.
66
67 ticks
68 The "ticks" method returns the number of intervals that the
69 top/bottom/size values will result in.
70
71 add_data
72 $self->add_data( @dataset );
73
74 The "add_data" method allows you to provide data that the object should
75 be aware of when calculating the axis. In fact, you can add additional
76 data at any time, and the axis will be updated as needed.
77
78 set_maximum_intervals
79 $self->set_maximum_intervals( $intervals );
80
81 The "set_maximum_intervals" method takes an argument and uses it as the
82 maximum number of ticks the axis is allowed to have.
83
84 include_zero
85 If you have a dataset something like ( 10, 11, 12 ) the bottom of the
86 axis will probably be somewhere around 9 or 8. That is, it won't show
87 the zero axis. If you want to force the axis to include zero, use this
88 method to do so.
89
90 apply_to
91 $self->apply_to( $gd_graph_object )
92
93 The "apply_to" method is intended to provide a series of shortcuts for
94 automatically applying an axis to a graph of a know type. At the
95 present, this will change only the Y axis of a GD::Graph object. This
96 method is considered experimental. If in doubt, extract and set the
97 graph values yourself.
98
99SUPPORT
100 Bugs should be reported via the CPAN bug tracker
101
102 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Chart-Math-Axis>
103
104 For other issues, or commercial enhancement or support, contact the
105 author.
106
107AUTHOR
108 Adam Kennedy <adamk@cpan.org>
109
110SEE ALSO
111 GD::Graph, <http://ali.as/>
112
113COPYRIGHT
114 Copyright 2002 - 2011 Adam Kennedy.
115
116 This program is free software; you can redistribute it and/or modify it
117 under the same terms as Perl itself.
118
119 The full text of the license can be found in the LICENSE file included
120 with this module.
121
122