ChiSquaredDistribution: Use the gamma distribution to create a sampler.
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 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);
+ }
}
