Mercurial > octave-antonio
annotate scripts/special-matrix/wilkinson.m @ 12639:4d777e05d47c stable
doc: Review and update documentation for "Matrix Manipulation" chapter.
* matrix.txi, arrayfun.m, blkdiag.m, fliplr.m, flipud.m, logspace.m,
postpad.m, prepad.m, randi.m, repmat.m, rot90.m, rotdim.m, shiftdim.m,
sortrows.m, vech.m, xor.m, hadamard.m, hankel.m, hilb.m, invhilb.m, magic.m,
pascal.m, rosser.m, sylvester_matrix.m, toeplitz.m, vander.m, wilkinson.m,
bsxfun.cc, find.cc, lookup.cc, rand.cc, tril.cc, data.cc, arrayfun.m,
blkdiag.m, fliplr.m, flipud.m, logspace.m, postpad.m, prepad.m, randi.m,
repmat.m, rot90.m, rotdim.m, shiftdim.m, sortrows.m, vech.m, xor.m, hadamard.m,
hankel.m, hilb.m, invhilb.m, magic.m, pascal.m, rosser.m, sylvester_matrix.m,
toeplitz.m, vander.m, wilkinson.m, bsxfun.cc (bsxfun), find.cc (find),
lookup.cc (lookup), rand.cc (rand, randn, rande, randg, randp),
tril.cc (triu), data.cc (all, any, horzcat, vertcat, cat, permute, ipermute,
ones, zeros, eye, linspace, resize, reshape, issorted, diff):
Improve docstrings
| author | Rik <octave@nomad.inbox5.com> |
|---|---|
| date | Sun, 01 May 2011 08:55:15 -0700 |
| parents | e4a1ede4e832 |
| children | 3a2f28c08fbd |
| rev | line source |
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| 11523 | 1 ## Copyright (C) 1999-2011 Peter Ekberg |
| 5827 | 2 ## |
| 3 ## This file is part of Octave. | |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 5827 | 9 ## |
| 10 ## Octave is distributed in the hope that it will be useful, but | |
| 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 ## General Public License for more details. | |
| 14 ## | |
| 15 ## You should have received a copy of the GNU General Public License | |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 5827 | 18 |
| 19 ## -*- texinfo -*- | |
| 20 ## @deftypefn {Function File} {} wilkinson (@var{n}) | |
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21 ## Return the Wilkinson matrix of order @var{n}. Wilkinson matrices are |
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22 ## symmetric and tridiagonal with pairs of nearly, but not exactly, equal |
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23 ## eigenvalues. They are useful in testing the behavior and performance |
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24 ## of eigenvalue solvers. |
| 5827 | 25 ## |
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26 ## @seealso{rosser, eig} |
| 5827 | 27 ## @end deftypefn |
| 28 | |
| 29 ## Author: Peter Ekberg | |
| 30 ## (peda) | |
| 31 | |
| 32 function retval = wilkinson (n) | |
| 33 | |
| 34 if (nargin != 1) | |
| 35 print_usage (); | |
| 36 endif | |
| 37 | |
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38 if (! (isscalar (n) && (n == fix (n)) && n >= 0)) |
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39 error ("wilkinson: N must be a non-negative integer"); |
| 5827 | 40 endif |
| 41 | |
| 42 side = ones (n-1, 1); | |
| 43 center = abs (-(n-1)/2:(n-1)/2); | |
| 44 retval = diag (side, -1) + diag (center) + diag (side, 1); | |
| 45 | |
| 46 endfunction | |
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47 |
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48 %!assert (wilkinson(0), []) |
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49 %!assert (wilkinson(1), 0) |
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50 %!assert (wilkinson(2), [0.5,1;1,0.5]) |
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51 %!assert (wilkinson(3), [1,1,0;1,0,1;0,1,1]) |
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52 %!assert (wilkinson(4), [1.5,1,0,0;1,0.5,1,0;0,1,0.5,1;0,0,1,1.5]) |
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53 %!error (wilkinson()) |
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54 %!error (wilkinson(1,2)) |