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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: beta_rnd (a, b [, r, c])
##
## beta_rnd (a, b) returns a matrix of random samples from the Beta
## distribution with parameters a and b. The size of the matrix is the
## common size of a and b.
##
## beta_rnd (a, b, r, c) returns an r by c matrix of random samples from
## the Beta distribution with parameters a and b. Both a and b must be
## scalar or of size r by c.
## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Description: Random deviates from the Beta distribution
function rnd = beta_rnd (a, b, r, c)
if (nargin == 4)
if ( !(is_scalar (r) && (r > 0) && (r == round (r))) )
error ("beta_rnd: r must be a positive integer");
endif
if ( !(is_scalar (c) && (c > 0) && (c == round (c))) )
error ("beta_rnd: c must be a positive integer");
endif
[retval, a, b] = common_size (a, b, zeros (r, c));
if (retval > 0)
error (strcat("beta_rnd: ",
"a and b must be scalar or of size ",
sprintf ("%d by %d", r, c)));
endif
elseif (nargin == 2)
[retval, a, b] = common_size (a, b);
if (retval > 0)
error ("beta_rnd: a and b must be of common size or scalar");
endif
else
usage ("beta_rnd (a, b [, r, c])");
endif
[r, c] = size (a);
s = r * c;
a = reshape (a, 1, s);
b = reshape (b, 1, s);
rnd = zeros (1, s);
k = find (!(a > 0) | !(a < Inf) | !(b > 0) | !(b < Inf));
if (any (k))
rnd(k) = NaN * ones (1, length (k));
endif
k = find ((a > 0) & (a < Inf) & (b > 0) & (b < Inf));
if (any (k))
rnd(k) = beta_inv (rand (1, length (k)), a(k), b(k));
endif
rnd = reshape (rnd, r, c);
endfunction
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