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## Copyright (C) 1995, 1996, 1997 Kurt Hornik
##
## This program 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.
##
## This program 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 this file. If not, write to the Free Software Foundation,
## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
## usage: laplace_rnd (r, c)
##
## Return an r by c matrix of random numbers from the Laplace
## distribution.
## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Description: Random deviates from the Laplace distribution
function rnd = laplace_rnd (r, c)
if (nargin != 2)
usage ("laplace_rnd (r, c)");
endif
if ( !(is_scalar (r) && (r > 0) && (r == round (r))) )
error ("laplace_rnd: r must be a positive integer");
endif
if ( !(is_scalar (c) && (c > 0) && (c == round (c))) )
error ("laplace_rnd: c must be a positive integer");
endif
tmp = rand (r, c);
rnd = ((tmp < 1/2) .* log (2 * tmp)
- (tmp > 1/2) .* log (2 * (1 - tmp)));
endfunction
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