From a8e4d6eb6e386dc12fa586bd4a920546b505f17b Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Tue, 22 Mar 2011 15:55:51 -0700
Subject: Issue 10787: Document the probability density function for
 random.gammavariate.

---
 Lib/random.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Lib/random.py b/Lib/random.py
index 592e4b8..49f5859 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -470,6 +470,12 @@ class Random(_random.Random):
 
         Conditions on the parameters are alpha > 0 and beta > 0.
 
+        The probability distribution function is:
+
+                    x ** (alpha - 1) * math.exp(-x / beta)
+          pdf(x) =  --------------------------------------
+                      math.gamma(alpha) * beta ** alpha
+
         """
 
         # alpha > 0, beta > 0, mean is alpha*beta, variance is alpha*beta**2
-- 
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