1## Copyright (C) 2013-2020 Alexander Barth
2## Copyright (C) 2018-2020 Philip Nienhuis
3##
4## This program is free software; you can redistribute it and/or modify it under
5## the terms of the GNU General Public License as published by the Free Software
6## Foundation; either version 3 of the License, or (at your option) any later
7## version.
8##
9## This program is distributed in the hope that it will be useful, but WITHOUT
10## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
12## details.
13##
14## You should have received a copy of the GNU General Public License along with
15## this program; if not, see <http://www.gnu.org/licenses/>.
16
17## -*- texinfo -*-
18## @deftypefn  {Function File} {@var{sm} =} deg2sm (@var{deg})
19## @deftypefnx {Function File} {@var{sm} =} deg2sm (@var{deg}, @var{radius})
20## @deftypefnx {Function File} {@var{sm} =} deg2sm (@var{deg}, @var{sphere})
21## Converts angle n degrees to distance in statute miles by multiplying angle
22## with radius.
23##
24## Calculates the distances @var{sm} in a sphere with @var{radius} (also in
25## statute miles) for the angles @var{deg}.  If unspecified, radius defaults to
26## 3958 sm, the mean radius of Earth.
27##
28## Alternatively, @var{sphere} can be one of "sun", "mercury", "venus", "earth",
29## "moon", "mars", "jupiter", "saturn", "uranus", "neptune", or "pluto", in
30## which case radius will be set to that object's mean radius.
31##
32## @seealso{deg2km, deg2nm, km2rad, km2deg,
33## nm2deg, nm2rad, rad2km, rad2nm, rad2sm, sm2deg, sm2rad}
34## @end deftypefn
35
36## Built with insight from
37## Author: Alexander Barth <barth.alexander@gmail.com>
38## Adapted from deg2km.m by Anonymous contributor, see patch #9709
39
40function sm = deg2sm (deg, radius = "earth")
41
42  ## Check arguments
43  if (nargin < 1 || nargin > 2)
44    print_usage();
45  elseif (ischar (radius))
46    ## Get radius of sphere with its default units (km)
47    radius = km2sm (spheres_radius (radius));
48  ## Check input
49  elseif (! isnumeric (radius) || ! isreal (radius))
50    error ("deg2sm: RADIUS must be a numeric scalar");
51  endif
52  sm = (deg2rad (deg) * radius);
53
54endfunction
55
56
57%!test
58%!assert (sm2deg (deg2sm (10)), 10, 10*eps);
59%!assert (sm2deg (deg2sm (10, 80), 80), 10, 10*eps);
60%!assert (sm2deg (deg2sm (10, "pluto"), "pluto"), 10, 10*eps);
61
62%!error <RADIUS> deg2sm (5, 5i)
63