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########################################################################
##
## Copyright (C) 1999-2026 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave 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 3 of the License, or
## (at your option) any later version.
##
## Octave 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 Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{map} =} flag ()
## @deftypefnx {} {@var{map} =} flag (@var{n})
## Create color colormap. This colormap cycles through red, white, blue, and
## black with each index change.
##
## The argument @var{n} must be a scalar.
## If @var{n} is not specified the length of the current colormap is used. If
## there is no current colormap the default value of 256 is used.
## @seealso{colormap}
## @end deftypefn
function map = flag (n)
if (nargin == 1)
if (! (isscalar (n) && isreal (n) && n == fix (n)))
error ("flag: N must be a scalar integer");
endif
n = double (n);
else
hf = get (0, "currentfigure");
if (! isempty (hf))
n = rows (get (hf, "colormap"));
else
n = 256;
endif
endif
if (n == 1)
map = [1, 0, 0];
elseif (n > 1)
C = [1, 0, 0; 1, 1, 1; 0, 0, 1; 0, 0, 0];
map = C(rem (0:(n-1), 4) + 1, :);
else
map = zeros (0, 3);
endif
endfunction
%!demo
%! ## Show the 'flag' colormap profile and as an image
%! cmap = flag (12); # 4 colors, therefore cycle 3 times
%! subplot (2, 1, 1);
%! rgbplot (cmap, "composite");
%! subplot (2, 1, 2);
%! rgbplot (cmap);
%!assert (size (flag ()), [256, 3])
%!assert (size (flag (16)), [16, 3])
%!assert (flag (1), [1, 0, 0])
%!assert (flag (true), double ([1, 0, 0]))
%!assert (flag (char (1)), double ([1, 0, 0]))
%!assert (flag (int32 (1)), double ([1, 0, 0]))
%!assert (flag (0), zeros (0, 3))
%!assert (flag (-1), zeros (0, 3))
%!test
%! a = [1, 0, 0;
%! 1, 1, 1;
%! 0, 0, 1;
%! 0, 0, 0;
%! 1, 0, 0;
%! 1, 1, 1;
%! 0, 0, 1;
%! 0, 0, 0;
%! 1, 0, 0;
%! 1, 1, 1;
%! 0, 0, 1;
%! 0, 0, 0];
%! assert (flag (12), a, eps);
## Input validation
%!error <N must be a scalar integer> flag ("foo")
%!error <N must be a scalar integer> flag ([1, 2, 3])
%!error <N must be a scalar integer> flag ({1, 2, 3})
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