1 files changed, 67 insertions, 0 deletions
diff --git a/gsl-1.9/randist/geometric.c b/gsl-1.9/randist/geometric.c
new file mode 100644
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+++ b/gsl-1.9/randist/geometric.c
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+/* randist/geometric.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>
+
+/* Geometric distribution (bernoulli trial with probability p) 
+
+   prob(k) =  p (1 - p)^(k-1) for n = 1, 2, 3, ...
+
+   It gives the distribution of "waiting times" for an event that
+   occurs with probability p. */
+
+unsigned int
+gsl_ran_geometric (const gsl_rng * r, const double p)
+{
+  double u = gsl_rng_uniform_pos (r);
+
+  unsigned int k;
+
+  if (p == 1)
+    {
+      k = 1;
+    }
+  else
+    {
+      k = log (u) / log (1 - p) + 1;
+    }
+
+  return k;
+}
+
+double
+gsl_ran_geometric_pdf (const unsigned int k, const double p)
+{
+  if (k == 0)
+    {
+      return 0 ;
+    }
+  else if (k == 1)
+    {
+      return p ;
+    }
+  else
+    {
+      double P = p * pow (1 - p, k - 1.0);
+      return P;
+    }
+}