1 ## Copyright (C) 1999-2012 Kai Habel
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {@var{map} =} rainbow ()
21 ## @deftypefnx {Function File} {@var{map} =} rainbow (@var{n})
22 ## Create color colormap. This colormap ranges from red through orange,
23 ## yellow, green, blue, to violet.
24 ## The argument @var{n} must be a scalar.
25 ## If unspecified, the length of the current colormap, or 64, is used.
29 ## Author: Kai Habel <kai.habel@gmx.de>
31 ## this colormap is not part of matlab, it is like the prism
32 ## colormap map but with a continuous map
34 function map = rainbow (n)
40 error ("rainbow: argument must be a scalar");
49 x = linspace (0, 1, n)';
50 r = (x < 2/5) + (x >= 2/5 & x < 3/5) .* (-5 * x + 3)\
51 + (x >= 4/5) .* (10/3 * x - 8/3);
52 g = (x < 2/5) .* (5/2 * x) + (x >= 2/5 & x < 3/5)\
53 + (x >= 3/5 & x < 4/5) .* (-5 * x + 4);
54 b = (x >= 3/5 & x < 4/5) .* (5 * x - 3) + (x >= 4/5);
63 %! ## Show the 'rainbow' colormap as an image
64 %! image (1:64, linspace (0, 1, 64), repmat (1:64, 64, 1)')
65 %! axis ([1, 64, 0, 1], "ticy", "xy")
66 %! colormap (rainbow (64))