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## Copyright (C) 1998, 1999, 2000 Joao Cardoso.
##
## 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.
##
## This file is part of plplot_octave.
function [gx gy] = gradn(z, dx, dy, order)
# [gx gy] = gradn(z, [dx, dy [,order]])
#
# gx and gy are the x and y components of the gradient of matrix z.
# dx and dy are scalars giving the x and y step of z, default to 1
# order is the order of the "gradient", default 1, max 4
if (nargin == 1)
dx = dy = 1;
endif
if (nargin == 3)
order = 1;
endif
if (nargin == 2 || nargin > 4)
help grad; return
endif
[nr nc] = size(z);
if (nr == 1 || nc == 1)
help gradn; return
endif
gx = gy = zeros(nr,nc);
for i=1:nr
gx(i,:) = diffn(z(i,:), dx, order);
endfor
for i=1:nc
gy(:,i) = diffn(z(:,i), dy, order);
endfor
endfunction
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