1 files changed, 50 insertions, 0 deletions
diff --git a/gsl-1.9/randist/pascal.c b/gsl-1.9/randist/pascal.c
new file mode 100644
index 0000000..58e25b5
--- /dev/null
+++ b/gsl-1.9/randist/pascal.c
@@ -0,0 +1,50 @@
+/* randist/pascal.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 James Theiler, Brian Gough
+ * 
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <config.h>
+#include <math.h>
+#include <gsl/gsl_rng.h>
+#include <gsl/gsl_randist.h>
+
+/* The Pascal distribution is a negative binomial with valued integer n
+
+   prob(k) =  (n - 1 + k)!/(n!(k - 1)!) *  p^n (1-p)^k for k = 0, 1, ..., n
+
+   */
+
+unsigned int
+gsl_ran_pascal (const gsl_rng * r, double p, unsigned int n)
+{
+  /* This is a separate interface for the pascal distribution so that
+     it can be optimized differently from the negative binomial in
+     future.
+     
+     e.g. if n < 10 it might be faster to generate the Pascal
+     distributions as the sum of geometric variates directly.  */
+  
+  unsigned int k = gsl_ran_negative_binomial (r, p, (double) n);
+  return k;
+}
+
+double
+gsl_ran_pascal_pdf (const unsigned int k, const double p, unsigned int n)
+{
+  double P = gsl_ran_negative_binomial_pdf (k, p, (double) n);
+  return P;
+}