[commons-statistics] branch master updated: ChiSquaredDistribution: Use the gamma distribution to create a sampler.

[aherbert]

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aherbert pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-statistics.git


The following commit(s) were added to refs/heads/master by this push:
     new f685029  ChiSquaredDistribution: Use the gamma distribution to create 
a sampler.
f685029 is described below

commit f685029b9c6eb33f090e084e4ed96faa11cd0b93
Author: Alex Herbert <aherb...@apache.org>
AuthorDate: Wed Oct 2 23:32:50 2019 +0100

    ChiSquaredDistribution: Use the gamma distribution to create a sampler.
---
 .../distribution/ChiSquaredDistribution.java       | 31 ++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git 
a/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/ChiSquaredDistribution.java
 
b/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/ChiSquaredDistribution.java
index 3407cc6..e012281 100644
--- 
a/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/ChiSquaredDistribution.java
+++ 
b/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/ChiSquaredDistribution.java
@@ -16,6 +16,8 @@
  */
 package org.apache.commons.statistics.distribution;
 
+import org.apache.commons.rng.UniformRandomProvider;
+
 /**
  * Implementation of the <a 
href="http://en.wikipedia.org/wiki/Chi-squared_distribution";>chi-squared 
distribution</a>.
  */
@@ -116,4 +118,33 @@ public class ChiSquaredDistribution extends 
AbstractContinuousDistribution {
     public boolean isSupportConnected() {
         return true;
     }
+
+    /**
+     * {@inheritDoc}
+     *
+     * <p>
+     * Sampling algorithms:
+     * <ul>
+     *  <li>
+     *   For {@code 0 < degreesOfFreedom < 2}:
+     *   <blockquote>
+     *    Ahrens, J. H. and Dieter, U.,
+     *    <i>Computer methods for sampling from gamma, beta, Poisson and 
binomial distributions,</i>
+     *    Computing, 12, 223-246, 1974.
+     *   </blockquote>
+     *  </li>
+     *  <li>
+     *  For {@code degreesOfFreedom >= 2}:
+     *   <blockquote>
+     *   Marsaglia and Tsang, <i>A Simple Method for Generating
+     *   Gamma Variables.</i> ACM Transactions on Mathematical Software,
+     *   Volume 26 Issue 3, September, 2000.
+     *   </blockquote>
+     *  </li>
+     * </ul>
+     */
+    @Override
+    public ContinuousDistribution.Sampler createSampler(final 
UniformRandomProvider rng) {
+        return gamma.createSampler(rng);
+    }
 }