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1 ## Copyright (C) 1999, 2006, 2007 Peter Ekberg |
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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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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} wilkinson (@var{n}) |
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21 ## |
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22 ## Return the Wilkinson matrix of order @var{n}. |
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23 ## |
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24 ## @seealso{hankel, vander, sylvester_matrix, hilb, invhilb, toeplitz |
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25 ## hadamard, rosser, compan, pascal} |
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26 ## @end deftypefn |
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27 |
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28 ## Author: Peter Ekberg |
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29 ## (peda) |
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30 |
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31 function retval = wilkinson (n) |
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32 |
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33 if (nargin != 1) |
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34 print_usage (); |
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35 endif |
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36 |
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37 nmax = length (n); |
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38 if (! (nmax == 1)) |
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39 error ("wilkinson: expecting scalar argument, found something else"); |
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40 endif |
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41 |
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42 side = ones (n-1, 1); |
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43 center = abs (-(n-1)/2:(n-1)/2); |
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44 retval = diag (side, -1) + diag (center) + diag (side, 1); |
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45 |
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46 endfunction |
