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comparison scripts/special-matrix/wilkinson.m @ 5827:1fe78adb91bc

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[project @ 2006-05-22 06:25:14 by jwe]
author jwe
date Mon, 22 May 2006 06:25:14 +0000
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children 93c65f2a5668
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5826:6c6ff9b82577 5827:1fe78adb91bc
1 ## Copyright (C) 1999 Peter Ekberg
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
7 ## the Free Software Foundation; either version 2, or (at your option)
8 ## any later version.
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
16 ## along with Octave; see the file COPYING. If not, write to the Free
17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 ## 02110-1301, USA.
19
20 ## -*- texinfo -*-
21 ## @deftypefn {Function File} {} wilkinson (@var{n})
22 ##
23 ## Return the Wilkinson matrix of order @var{n}.
24 ##
25 ## @seealso{hankel, vander, sylvester_matrix, hilb, invhilb, toeplitz
26 ## hadamard, rosser, compan, pascal}
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
38 nmax = length (n);
39 if (! (nmax == 1))
40 error ("wilkinson: expecting scalar argument, found something else");
41 endif
42
43 side = ones (n-1, 1);
44 center = abs (-(n-1)/2:(n-1)/2);
45 retval = diag (side, -1) + diag (center) + diag (side, 1);
46
47 endfunction