## Copyright (C) 1995, 1996, 1997  Kurt Hornik
##
## 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} {} geometric_rnd (@var{p}, @var{r}, @var{c})
## @deftypefnx {Function File} {} geometric_rnd (@var{p}, @var{sz})
## Return an @var{r} by @var{c} matrix of random samples from the
## geometric distribution with parameter @var{p}, which must be a scalar
## or of size @var{r} by @var{c}.
##
## If @var{r} and @var{c} are given create a matrix with @var{r} rows and
## @var{c} columns. Or if @var{sz} is a vector, create a matrix of size
## @var{sz}.
## @end deftypefn

## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Description: Random deviates from the geometric distribution

function rnd = geometric_rnd (p, r, c)

  if (nargin == 3)
    if (! (isscalar (r) && (r > 0) && (r == round (r))))
      error ("geometric_rnd: r must be a positive integer");
    endif
    if (! (isscalar (c) && (c > 0) && (c == round (c))))
      error ("geometric_rnd: c must be a positive integer");
    endif
    sz = [r, c];

    if (any (size (p) != 1) && ((length (size (p)) != length (sz)) ||
				any (size (p) != sz)))
      error ("geometric_rnd: p must be scalar or of size [r, c]");
    endif
  elseif (nargin == 2)
    if (isscalar (r) && (r > 0))
      sz = [r, r];
    elseif (isvector(r) && all (r > 0))
      sz = r(:)';
    else
      error ("geometric_rnd: r must be a postive integer or vector");
    endif

    if (any (size (p) != 1) && ((length (size (p)) != length (sz)) ||
				any (size (p) != sz)))
      error ("geometric_rnd: n must be scalar or of size sz");
    endif
  elseif (nargin == 1)
    sz = size(n);
  elseif (nargin != 1)
    usage ("geometric_rnd (p, r, c)");
  endif


  if (isscalar (p))
    if (!(p >= 0) || !(p <= 1))
      rnd = NaN * ones (sz);
    elseif (p == 0)
      rnd = Inf * ones (sz);
    elseif ((p > 0) & (p < 1));
      rnd = floor (log (rand (sz)) / log (1 - p));
    else
      rnd = zeros (sz);
    endif
  else
    rnd = zeros (sz);

    k = find (!(p >= 0) | !(p <= 1));
    if (any (k))
      rnd(k) = NaN * ones (1, length (k));
    endif

    k = find (p == 0);
    if (any (k))
      rnd(k) = Inf * ones (1, length (k));
    endif

    k = find ((p > 0) & (p < 1));
    if (any (k))
      rnd(k) = floor (log (rand (size (k))) ./ log (1 - p(k)));
    endif
  endif

endfunction