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uniform_rnd.m

## 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:  uniform_rnd (a, b [, r, c])
##
## uniform_rnd (a, b) returns a matrix of random samples from the
## uniform distribution on [a, b].  The size of the matrix is the common
## size of a and b.
##
## uniform_rnd (a, b, r, c) returns an r by c matrix of random samples
## from the uniform distribution on [a, 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 uniform distribution
  
function rnd = uniform_rnd (a, b, r, c)

  if (nargin == 4)
    if ( !(is_scalar (r) && (r > 0) && (r == round (r))) )
      error ("uniform_rnd:  r must be a positive integer");
    endif
    if ( !(is_scalar (c) && (c > 0) && (c == round (c))) )
      error ("uniform_rnd:  c must be a positive integer");
    endif
    [retval, a, b] = common_size (a, b, zeros (r, c));
    if (retval > 0)
      error (strcat("uniform_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 ("uniform_rnd:  a and b must be of common size or scalar");
    endif
  else
    usage ("uniform_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 (!(-Inf < a) | !(a < b) | !(b < Inf));
  if any (k)
    rnd(k) = NaN * ones (1, length (k));
  endif
  
  k = find ((-Inf < a) & (a < b) & (b < Inf));
  if any (k)
    rnd(k) = a(k) + (b(k) - a(k)) .* rand (1, length (k));
  endif
  
  rnd = reshape (rnd, r, c);
  
endfunction

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