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diff --git a/gsl-1.9/cdf/binomial.c b/gsl-1.9/cdf/binomial.c
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+/* cdf/binomial.c
+ * 
+ * Copyright (C) 2004 Jason H. Stover.
+ * Copyright (C) 2004 Giulio Bottazzi
+ * 
+ * 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 of the License, 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 program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+#include <math.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_cdf.h>
+#include <gsl/gsl_sf_gamma.h>
+
+#include "error.h"
+
+/* Computes the cumulative distribution function for a binomial
+   random variable. For a binomial random variable X with n trials
+   and success probability p,
+   
+           Pr( X <= k ) = Pr( Y >= p )
+ 
+   where Y is a beta random variable with parameters k+1 and n-k.
+ 
+   The binomial distribution has the form,
+
+   prob(k) =  n!/(k!(n-k)!) *  p^k (1-p)^(n-k) for k = 0, 1, ..., n
+
+   The cumulated distributions can be expressed in terms of normalized
+   incomplete beta functions (see Abramowitz & Stegun eq. 26.5.26 and
+   eq. 6.6.3).
+
+   Reference: 
+  
+   W. Feller, "An Introduction to Probability and Its
+   Applications," volume 1. Wiley, 1968. Exercise 45, page 173,
+   chapter 6.
+ */
+
+#include <config.h>
+#include <math.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_cdf.h>
+
+double
+gsl_cdf_binomial_P (const unsigned int k, const double p, const unsigned int n)
+{
+  double P;
+  double a;
+  double b;
+
+  if (p > 1.0 || p < 0.0)
+    {
+      CDF_ERROR ("p < 0 or p > 1", GSL_EDOM);
+    }
+
+  if (k >= n)
+    {
+      P = 1.0;
+    }
+  else
+    {
+      a = (double) k + 1.0;
+      b = (double) n - k;
+      P = gsl_cdf_beta_Q (p, a, b);
+    }
+
+  return P;
+}
+
+double
+gsl_cdf_binomial_Q (const unsigned int k, const double p, const unsigned int n)
+{
+  double Q;
+  double a;
+  double b;
+
+  if (p > 1.0 || p < 0.0)
+    {
+      CDF_ERROR ("p < 0 or p > 1", GSL_EDOM);
+    }
+
+  if (k >= n)
+    {
+      Q = 0.0;
+    }
+  else
+    {
+      a = (double) k + 1.0;
+      b = (double) n - k;
+      Q = gsl_cdf_beta_P (p, a, b);
+    }
+
+  return Q;
+}