view scripts/sparse/spalloc.m @ 7017:a1dbe9d80eee

[project @ 2007-10-12 21:27:11 by jwe]
author jwe
date Fri, 12 Oct 2007 21:27:37 +0000
parents 93c65f2a5668
children f084ba47812b
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## Copyright (C) 2004, 2005, 2006, 2007 David Bateman & Andy Adler
##
## 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 3 of the License, 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, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {@var{s} =} spalloc (@var{r}, @var{c}, @var{nz})
## Returns an empty sparse matrix of size @var{r}-by-@var{c}. As Octave
## resizes sparse matrices at the first opportunity, so that no additional 
## space is needed, the argument @var{nz} is ignored. This function is 
## provided only for compatibility reasons.
##
## It should be noted that this means that code like
##
## @example
## k = 5;
## nz = r * k;
## s = spalloc (r, c, nz)
## for j = 1:c
##   idx = randperm (r);
##   s (:, j) = [zeros(r - k, 1); rand(k, 1)] (idx);
## endfor
## @end example
##
## will reallocate memory at each step. It is therefore vitally important
## that code like this is vectorized as much as possible.
## @seealso{sparse, nzmax}
## @end deftypefn

function s = spalloc (r, c, nz)
  s = sparse (r, c);
endfunction