--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/statistics/distributions/hygepdf.m	Wed Jul 13 17:43:35 2005 +0000
@@ -0,0 +1,73 @@
+## Copyright (C) 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} {} hypergeometric_pdf (@var{x}, @var{m}, @var{t}, @var{n})
+## Compute the probability density function (PDF) at @var{x} of the
+## hypergeometric distribution with parameters @var{m}, @var{t}, and
+## @var{n}. This is the probability of obtaining @var{x} marked items
+## when randomly drawing a sample of size @var{n} without replacement
+## from a population of total size @var{t} containing @var{m} marked items.
+##
+## The arguments must be of common size or scalar.
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
+## Description: PDF of the hypergeometric distribution
+
+function pdf = hypergeometric_pdf (x, m, t, n)
+
+  if (nargin != 4)
+    usage ("hypergeometric_pdf (x, m, t, n)");
+  endif
+
+  if (!isscalar (m) || !isscalar (t) || !isscalar (n))
+    [retval, x, m, t, n] = common_size (x, m, t, n);
+    if (retval > 0)
+      error ("hypergeometric_pdf: x, m, t, and n must be of common size or scalar");
+    endif
+  endif
+
+  pdf = zeros (size (x));
+
+  ## everything in i1 gives NaN
+  i1 = ((m < 0) | (t < 0) | (n <= 0) | (m != round (m)) |
+        (t != round (t)) | (n != round (n)) | (m > t) | (n > t));
+  ## everything in i2 gives 0 unless in i1
+  i2 = ((x != round (x)) | (x < 0) | (x > m) | (n < x) | (n-x > t-m));
+  k = find (i1);
+  if (any (k))
+    if (isscalar (m) && isscalar (t) && isscalar (n))
+      pdf = NaN * ones ( size (x));
+    else
+      pdf (k) = NaN;
+    endif
+  endif
+  k = find (!i1 & !i2);
+  if (any (k))
+    if (isscalar (m) && isscalar (t) && isscalar (n))
+      pdf (k) = (bincoeff (m, x(k)) .* bincoeff (t-m, n-x(k))
+		 / bincoeff (t, n));
+    else
+      pdf (k) = (bincoeff (m(k), x(k)) .* bincoeff (t(k)-m(k), n(k)-x(k))
+		 ./ bincoeff (t(k), n(k)));
+    endif
+  endif
+
+endfunction