wilkinson.m

JAVA 数学程序库 提供常规的数值计算程序包

## Copyright (C) 1999 Peter Ekberg
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, write to the Free
## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301, USA.

## -*- texinfo -*-
## @deftypefn {Function File} {} wilkinson (@var{n})
##
## Return the Wilkinson matrix of order @var{n}.
##
## @seealso{hankel, vander, sylvester_matrix, hilb, invhilb, toeplitz
##           hadamard, rosser, compan, pascal}
## @end deftypefn

## Author: Peter Ekberg
##         (peda)

function retval = wilkinson (n)

  if (nargin != 1)
    print_usage ();
  endif

  nmax = length (n);
  if (! (nmax == 1))
    error ("wilkinson: expecting scalar argument, found something else");
  endif

  side = ones (n-1, 1);
  center = abs (-(n-1)/2:(n-1)/2);
  retval = diag (side, -1) + diag (center) + diag (side, 1);

endfunction

/*
@GROUP
specialmatrix
@SYNTAX
retval = wilkinson(n)
@DOC
.
@EXAMPLES
@NOTES
@SEE
*/