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1 # Copyright (C) 1993 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 the |
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7 # Free Software Foundation; either version 2, or (at your option) any |
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8 # later version. |
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9 # |
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10 # Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 # 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, write to the Free |
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17 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. |
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18 |
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4
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19 function retval = cond (a) |
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20 |
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21 # usage: cond (a) |
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22 # |
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23 # Return the condition number of a, computed using the singular values |
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24 # of a. |
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25 # |
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26 # See also: norm, svd |
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27 |
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28 if (nargin == 1) |
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29 [nr, nc] = size (a); |
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30 if (nr == 0 && nc == 0) |
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31 if (strcmp (propagate_empty_matrices, "false")) |
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32 error ("cond: empty matrix is invalid as argument"); |
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33 endif |
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34 if (strcmp (propagate_empty_matrices, "warn")) |
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35 printf ("warning: cond: argument is empty matrix\n"); |
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36 endif |
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37 retval = 0.0; |
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38 endif |
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39 sigma = svd (a); |
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40 retval = sigma (1) / sigma (length (sigma)); |
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41 else |
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42 error ("usage: cond (a)"); |
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43 endif |
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44 |
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45 endfunction |
