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annotate scripts/linear-algebra/trace.m @ 11542:695141f1c05c ss-3-3-55

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snapshot 3.3.55
author John W. Eaton <jwe@octave.org>
date Sat, 15 Jan 2011 04:53:04 -0500
parents fd0a3ac60b0e
children 72c96de7a403
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1 ## Copyright (C) 1993-2011 John W. Eaton
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {} trace (@var{A})
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21 ## Compute the trace of @var{A}, @code{sum (diag (@var{A}))}.
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22 ## @end deftypefn
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24 ## Author: jwe
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25
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26 function y = trace (A)
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28 if (nargin != 1)
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29 print_usage ();
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30 endif
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31
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32 if (ndims (A) > 2)
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33 error ("trace: only valid on 2-D objects");
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34 elseif (isempty (A))
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35 y = 0;
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36 elseif (any (size (A) == 1))
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37 y = A(1);
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38 else
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39 y = sum (diag (A));
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40 endif
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42 endfunction
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44 %!assert(trace ([1, 2; 3, 4]) == 5);
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45 %!assert(trace ([1, 2; 3, 4; 5, 6]) == 5);
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46 %!assert(trace ([1, 3, 5; 2, 4, 6]) == 5);
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47 %!assert(trace ([]), 0);
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48 %!assert(trace (randn(1,0)), 0);
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49 %!
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50 %!error trace ();
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51 %!error trace (1, 2);
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52 %!error <only valid on 2-D objects> trace(reshape(1:9,[1,3,3]));