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annotate scripts/linear-algebra/issymmetric.m @ 11431:0d9640d755b1

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Improve docstrings for all isXXX functions. Use 'return true' rather than 'return 1'. Improve the cross-referencing through seealso links.
author Rik <octave@nomad.inbox5.com>
date Fri, 31 Dec 2010 13:20:44 -0800
parents fbd7843974fa
children fd0a3ac60b0e
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John W. Eaton <jwe@octave.org>
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1 ## Copyright (C) 1996, 1997, 2002, 2003, 2004, 2005, 2006, 2007, 2008
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2 ## John W. Eaton
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3 ## Copyright (C) 2009 VZLU Prague
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4 ##
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5 ## This file is part of Octave.
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6 ##
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7 ## Octave is free software; you can redistribute it and/or modify it
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8 ## under the terms of the GNU General Public License as published by
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9 ## the Free Software Foundation; either version 3 of the License, or (at
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10 ## your option) any later version.
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11 ##
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12 ## Octave is distributed in the hope that it will be useful, but
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13 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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14 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 ## General Public License for more details.
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16 ##
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17 ## You should have received a copy of the GNU General Public License
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18 ## along with Octave; see the file COPYING. If not, see
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19 ## <http://www.gnu.org/licenses/>.
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20
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21 ## -*- texinfo -*-
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22 ## @deftypefn {Function File} {} issymmetric (@var{x})
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23 ## @deftypefnx {Function File} {} issymmetric (@var{x}, @var{tol})
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24 ## Return true if @var{x} is a symmetric matrix within the tolerance specified
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25 ## by @var{tol}. The default tolerance is zero (uses faster code).
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26 ## Matrix @var{x} is considered symmetric if
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27 ## @code{norm (@var{x} - @var{x}.', Inf) / norm (@var{x}, Inf) < @var{tol}}.
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28 ## @seealso{ishermitian, isdefinite}
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29 ## @end deftypefn
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30
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31 ## Author: A. S. Hodel <scotte@eng.auburn.edu>
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32 ## Created: August 1993
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33 ## Adapted-By: jwe
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34
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35 function retval = issymmetric (x, tol = 0)
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36
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37 if (nargin < 1 || nargin > 2)
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38 print_usage ();
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39 endif
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40
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41 retval = isnumeric (x) && issquare (x);
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42 if (retval)
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43 if (tol == 0)
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44 retval = all ((x == x.')(:));
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45 else
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46 norm_x = norm (x, inf);
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47 retval = norm_x == 0 || norm (x - x.', inf) / norm_x <= tol;
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48 endif
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49 endif
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50
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51 endfunction
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52
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53 %!assert(issymmetric (1));
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54 %!assert(!(issymmetric ([1, 2])));
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55 %!assert(issymmetric ([]));
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56 %!assert(issymmetric ([1, 2; 2, 1]));
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57 %!assert(!(issymmetric ("test")));
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58 %!assert(issymmetric ([1, 2.1; 2, 1.1], 0.2));
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59 %!assert(issymmetric ([1, 2i; 2i, 1]));
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60 %!assert(!(issymmetric ("t")));
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61 %!assert(!(issymmetric (["te"; "et"])));
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62 %!error issymmetric ([1, 2; 2, 1], 0, 0);
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63 %!error issymmetric ();
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64
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65 %!test
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66 %! s.a = 1;
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67 %! assert(!(issymmetric (s)));