## Copyright (C) 1998-2004 Andy Adler
##
## 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., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301  USA

## -*- texinfo -*-
## @deftypefn {Function File} {} spy (@var{x})
## Plot the sparsity pattern of the sparse matrix @var{x}.
## @end deftypefn

function spy (S) 

  if (issparse (S))
    [i, j, s, m, n] = spfind (S);
  else
    [i, j, s] = find (S);
    [m, n] = size (S);
  endif

  if (numel (i) < 1000)
    plot (j, i, "*");
  else
    plot (j, i, ".");
  endif

  axis ([0, n+1, m+1, 0]);

endfunction