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+/* gammadist.h -- computes probability of samples under / produces samples from a Gamma distribution
+ *
+ * Mark Johnson, 22nd March 2008
+ *
+ * gammavariate() was translated from random.py in Python library
+ *
+ * The Gamma distribution is:
+ *
+ * Gamma(x | alpha, beta) = pow(x/beta, alpha-1) * exp(-x/beta) / (gamma(alpha)*beta)
+ *
+ * shape parameter alpha > 0 (also called c), scale parameter beta > 0 (also called s);
+ * mean is alpha*beta, variance is alpha*beta**2
+ *
+ * Note that many parameterizations of the Gamma function are in terms of an _inverse_
+ * scale parameter beta, which is the inverse of the beta given here.
+ */
+
+#ifndef GAMMADIST_H
+#define GAMMADIST_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+ /* gammadist() returns the probability density of x under a Gamma(alpha,beta)
+ * distribution
+ */
+
+ long double gammadist(long double x, long double alpha, long double beta);
+
+ /* lgammadist() returns the log probability density of x under a Gamma(alpha,beta)
+ * distribution
+ */
+
+ long double lgammadist(long double x, long double alpha, long double beta);
+
+ /* gammavariate() generates samples from a Gamma distribution
+ * conditioned on the parameters alpha and beta.
+ *
+ * alpha > 0, beta > 0, mean is alpha*beta, variance is alpha*beta**2
+ *
+ * Warning: a few older sources define the gamma distribution in terms
+ * of alpha > -1.0
+ */
+
+ long double gammavariate(long double alpha, long double beta);
+
+ /* betadist() returns the probability density of x under a Beta(alpha,beta)
+ * distribution.
+ */
+
+ long double betadist(long double x, long double alpha, long double beta);
+
+ /* lbetadist() returns the log probability density of x under a Beta(alpha,beta)
+ * distribution.
+ */
+
+ long double lbetadist(long double x, long double alpha, long double beta);
+
+ /* betavariate() generates a sample from a Beta distribution with
+ * parameters alpha and beta.
+ *
+ * 0 < alpha < 1, 0 < beta < 1, mean is alpha/(alpha+beta)
+ */
+
+ long double betavariate(long double alpha, long double beta);
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif /* GAMMADIST_H */