update packages

[CreaPhase.git] / octave_packages / m / linear-algebra / issymmetric.m

diff --git a/octave_packages/m/linear-algebra/issymmetric.m b/octave_packages/m/linear-algebra/issymmetric.m
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+## Copyright (C) 1996-2012 John W. Eaton
+## Copyright (C) 2009 VZLU Prague
+##
+## 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} {} issymmetric (@var{x})
+## @deftypefnx {Function File} {} issymmetric (@var{x}, @var{tol})
+## Return true if @var{x} is a symmetric matrix within the tolerance specified
+## by @var{tol}.  The default tolerance is zero (uses faster code).
+## Matrix @var{x} is considered symmetric if
+## @code{norm (@var{x} - @var{x}.', Inf) / norm (@var{x}, Inf) < @var{tol}}.
+## @seealso{ishermitian, isdefinite}
+## @end deftypefn
+
+## Author: A. S. Hodel <scotte@eng.auburn.edu>
+## Created: August 1993
+## Adapted-By: jwe
+
+function retval = issymmetric (x, tol = 0)
+
+  if (nargin < 1 || nargin > 2)
+    print_usage ();
+  endif
+
+  retval = isnumeric (x) && issquare (x);
+  if (retval)
+    if (tol == 0)
+      retval = all ((x == x.')(:));
+    else
+      norm_x = norm (x, inf);
+      retval = norm_x == 0 || norm (x - x.', inf) / norm_x <= tol;
+    endif
+  endif
+
+endfunction
+
+%!assert(issymmetric (1));
+%!assert(!(issymmetric ([1, 2])));
+%!assert(issymmetric ([]));
+%!assert(issymmetric ([1, 2; 2, 1]));
+%!assert(!(issymmetric ("test")));
+%!assert(issymmetric ([1, 2.1; 2, 1.1], 0.2));
+%!assert(issymmetric ([1, 2i; 2i, 1]));
+%!assert(!(issymmetric ("t")));
+%!assert(!(issymmetric (["te"; "et"])));
+%!error issymmetric ([1, 2; 2, 1], 0, 0);
+%!error issymmetric ();
+
+%!test
+%! s.a = 1;
+%! assert(!(issymmetric (s)));