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1 ## Copyright (C) 1996, 1997, 2002, 2003, 2004, 2005, 2006, 2007 |
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2 ## John W. Eaton |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} issymmetric (@var{x}, @var{tol}) |
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22 ## If @var{x} is symmetric within the tolerance specified by @var{tol}, |
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23 ## then return the dimension of @var{x}. Otherwise, return 0. If |
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24 ## @var{tol} is omitted, use a tolerance equal to the machine precision. |
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25 ## Matrix @var{x} is considered symmetric if |
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26 ## @code{norm (@var{x} - @var{x}.', inf) / norm (@var{x}, inf) < @var{tol}}. |
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27 ## @seealso{size, rows, columns, length, ishermitian, ismatrix, isscalar, |
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28 ## issquare, isvector} |
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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) |
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36 |
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37 if (nargin == 1 || nargin == 2) |
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38 retval = issquare (x); |
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39 if (retval != 0) |
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40 if (nargin == 1) |
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41 tol = eps; |
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42 endif |
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43 norm_x = norm (x, inf); |
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44 if (norm_x != 0 && norm (x - x.', inf) / norm_x > tol) |
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45 retval = 0; |
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46 endif |
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47 endif |
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48 else |
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49 print_usage (); |
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50 endif |
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51 |
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52 endfunction |
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53 |
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54 %!assert(issymmetric (1)); |
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55 %!assert(!(issymmetric ([1, 2]))); |
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56 %!assert(!(issymmetric ([]))); |
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57 %!assert(issymmetric ([1, 2; 2, 1]) == 2); |
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58 %!assert(!(issymmetric ("test"))); |
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59 %!assert(issymmetric ([1, 2.1; 2, 1.1], 0.2) == 2); |
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60 %!assert(!issymmetric ([1, 2i; -2i, 1])); |
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61 %!assert(!(issymmetric ("t"))); |
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62 %!assert(!(issymmetric (["te"; "et"]))); |
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63 %!error issymmetric ([1, 2; 2, 1], 0, 0); |
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64 %!error issymmetric (); |
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65 |
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66 %!test |
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67 %! s.a = 1; |
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68 %! assert(!(issymmetric (s))); |
