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## Copyright (C) 1998-2013 Andy Adler
##
## 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
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {} spy (@var{x})
## @deftypefnx {Function File} {} spy (@dots{}, @var{markersize})
## @deftypefnx {Function File} {} spy (@dots{}, @var{line_spec})
## Plot the sparsity pattern of the sparse matrix @var{x}.
##
## If the argument @var{markersize} is given as a scalar value, it is used to
## determine the point size in the plot. If the string @var{line_spec} is
## given it is passed to @code{plot} and determines the appearance of the plot.
## @seealso{plot, gplot}
## @end deftypefn
function spy (x, varargin)
if (nargin < 1)
print_usage ();
endif
markersize = NaN;
if (nnz (x) < 1000)
line_spec = "*";
else
line_spec = ".";
endif
for i = 1:length (varargin)
if (ischar (varargin{i}))
if (length (varargin{i}) == 1)
line_spec = [line_spec, varargin{i}];
else
line_spec = varargin{i};
endif
elseif (isscalar (varargin{i}))
markersize = varargin{i};
else
error ("spy: expected markersize or linespec");
endif
endfor
[i, j, s] = find (x);
[m, n] = size (x);
if (isnan (markersize))
plot (j, i, line_spec);
else
plot (j, i, line_spec, "markersize", markersize);
endif
axis ([0, n+1, 0, m+1], "ij");
endfunction
%!demo
%! clf;
%! spy (sprand (10,10, 0.2));
%% Mark graphical function as tested by demo block
%!assert (1)
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