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rainbow.m    57 lines (50 with data), 1.9 kB

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## Copyright (C) 1999,2000 Kai Habel
##
## 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
## -*- texinfo -*-
## @deftypefn {Function File} {} rainbow (@var{n})
## Create color colormap.
## (red through orange, yellow, green, blue to violet)
## The argument @var{n} should be a scalar. If it
## is omitted, the length of the current colormap or 64 is assumed.
## @end deftypefn
## @seealso{colormap}
## Author: Kai Habel <kai.habel@gmx.de>
function map = rainbow (number)
## this colormap is not part of matlab, it is like the prism
## colormap map but with a continuous map
if (nargin == 0)
number = rows (colormap);
elseif (nargin == 1)
if (! is_scalar (number))
error ("rainbow: argument must be a scalar");
endif
else
usage ("rainbow (number)");
endif
if (number == 1)
map = [1, 0, 0];
elseif (number > 1)
x = linspace (0, 1, number)';
r = (x < 2/5) + (x >= 2/5 & x < 3/5) .* (-5 * x + 3)\
+ (x >= 4/5) .* (10/3 * x - 8/3);
g = (x < 2/5) .* (5/2 * x) + (x >= 2/5 & x < 3/5)\
+ (x >= 3/5 & x < 4/5) .* (-5 * x + 4);
b = (x >= 3/5 & x < 4/5) .* (5 * x - 3) + (x >= 4/5);
map = [r, g, b];
else
map = [];
endif
endfunction