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1 ## Copyright (C) 1993, 1994, 1995, 1996, 1997, 1999, 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} {} trace (@var{a}) |
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22 ## Compute the trace of @var{a}, @code{sum (diag (@var{a}))}. |
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23 ## @end deftypefn |
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24 |
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25 ## Author: jwe |
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26 |
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27 function y = trace (x) |
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28 |
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29 if (nargin != 1) |
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30 print_usage (); |
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31 endif |
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32 |
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33 if (ndims (x) > 2) |
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34 error ("trace: only valid on 2-D objects"); |
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35 elseif (isempty (x)) |
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36 y = 0; |
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37 elseif (any (size (x) == 1)) |
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38 y = x(1); |
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39 else |
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40 y = sum (diag (x)); |
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41 endif |
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42 |
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43 endfunction |
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44 |
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45 %!assert(trace ([1, 2; 3, 4]) == 5); |
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46 %!assert(trace ([1, 2; 3, 4; 5, 6]) == 5); |
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47 %!assert(trace ([1, 3, 5; 2, 4, 6]) == 5); |
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48 %!error trace (); |
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49 %!error trace (1, 2); |
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50 |
