1 files changed, 74 insertions, 0 deletions
diff --git a/gsl-1.9/cdf/gamma.c b/gsl-1.9/cdf/gamma.c
new file mode 100644
index 0000000..8174408
--- /dev/null
+++ b/gsl-1.9/cdf/gamma.c
@@ -0,0 +1,74 @@
+/* cdf/cdf_gamma.c
+ * 
+ * Copyright (C) 2003 Jason Stover.
+ * 
+ * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+/* 
+ * Author: J. Stover
+ */
+
+#include <config.h>
+#include <math.h>
+#include <gsl/gsl_cdf.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_sf_gamma.h>
+
+double
+gsl_cdf_gamma_P (const double x, const double a, const double b)
+{
+  double P;
+  double y = x / b;
+
+  if (x <= 0.0)
+    {
+      return 0.0;
+    }
+
+  if (y > a)
+    {
+      P = 1 - gsl_sf_gamma_inc_Q (a, y);
+    }
+  else
+    {
+      P = gsl_sf_gamma_inc_P (a, y);
+    }
+
+  return P;
+}
+
+double
+gsl_cdf_gamma_Q (const double x, const double a, const double b)
+{
+  double Q;
+  double y = x / b;
+
+  if (x <= 0.0)
+    {
+      return 1.0;
+    }
+
+  if (y < a)
+    {
+      Q = 1 - gsl_sf_gamma_inc_P (a, y);
+    }
+  else
+    {
+      Q = gsl_sf_gamma_inc_Q (a, y);
+    }
+
+  return Q;
+}