--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/statistics/distributions/poisson_cdf.m	Fri Oct 23 05:44:01 1998 +0000
@@ -0,0 +1,60 @@
+## 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:  poisson_cdf (x, lambda)
+##
+## For each element of x, compute the cumulative distribution function
+## (CDF) at x of the Poisson distribution with parameter lambda.
+
+## Author:  KH <Kurt.Hornik@ci.tuwien.ac.at>
+## Description:  CDF of the Poisson distribution
+
+function cdf = poisson_cdf (x, l)
+  
+  if (nargin != 2)
+    usage ("poisson_cdf (x, lambda)");
+  endif
+  
+  [retval, x, l] = common_size (x, l);
+  if (retval > 0)
+    error (["poisson_cdf:  ",
+	    "x and lambda must be of common size or scalar"]);
+  endif
+  
+  [r, c] = size (x);
+  s = r * c;
+  x = reshape (x, 1, s);
+  l = reshape (l, 1, s);
+  cdf = zeros (1, s);
+  
+  k = find (isnan (x) | !(l > 0));
+  if any (k)
+    cdf(k) = NaN * ones (1, length (k));
+  endif
+  
+  k = find ((x == Inf) & (l > 0));
+  if any (k)
+    cdf(k) = ones (1, length (k));
+  endif
+  
+  k = find ((x >= 0) & (x < Inf) & (l > 0));
+  if any (k)
+    cdf(k) = 1 - gammai (floor (x(k)) + 1, l(k));
+  endif
+
+  cdf = reshape (cdf, r, c);
+  
+endfunction