Feature/issue 3121 beta neg binomial rng

stan/math/prim/prob.hpp

@@ -29,6 +29,7 @@
 #include <stan/math/prim/prob/beta_neg_binomial_lccdf.hpp>
 #include <stan/math/prim/prob/beta_neg_binomial_lcdf.hpp>
 #include <stan/math/prim/prob/beta_neg_binomial_lpmf.hpp>
+#include <stan/math/prim/prob/beta_neg_binomial_rng.hpp>
 #include <stan/math/prim/prob/beta_proportion_ccdf_log.hpp>
 #include <stan/math/prim/prob/beta_proportion_cdf_log.hpp>
 #include <stan/math/prim/prob/beta_proportion_lccdf.hpp>

stan/math/prim/prob/beta_neg_binomial_rng.hpp

@@ -0,0 +1,67 @@
+#ifndef STAN_MATH_PRIM_PROB_BETA_NEG_BINOMIAL_RNG_HPP
+#define STAN_MATH_PRIM_PROB_BETA_NEG_BINOMIAL_RNG_HPP
+
+#include <stan/math/prim/meta.hpp>
+#include <stan/math/prim/prob/neg_binomial_rng.hpp>
+#include <stan/math/prim/prob/beta_rng.hpp>
+
+namespace stan {
+namespace math {
+
+/** \ingroup prob_dists
+ * Return a beta-negative binomial random variate with given number of
+ * successes, prior success, and prior failure parameters, using the given
+ * random number generator.
+ *
+ * r, alpha, and beta can each be a scalar or a one-dimensional container. Any
+ * non-scalar inputs must be the same size.
+ *
+ * @tparam T_r type of number of successes parameter
+ * @tparam T_alpha type of prior success parameter
+ * @tparam T_beta type of prior failure parameter
+ * @tparam RNG type of random number generator
+ *
+ * @param r (Sequence of) number of successes parameter(s)
+ * @param alpha (Sequence of) positive success parameter(s)
+ * @param beta (Sequence of) positive failure parameter(s)
+ * @param rng random number generator
+ * @return (Sequence of) beta-binomial random variate(s)
+ * @throw std::domain_error if r is negative, or alpha or beta are nonpositive
+ * @throw std::invalid_argument if non-scalar arguments are of different sizes
+ */
+template <typename T_r, typename T_alpha, typename T_beta, class RNG>
+inline typename VectorBuilder<true, int, T_r, T_alpha, T_beta>::type
+beta_neg_binomial_rng(const T_r &r, const T_alpha &alpha, const T_beta &beta,
+                      RNG &rng) {
+  using T_r_ref = ref_type_t<T_r>;
+  using T_alpha_ref = ref_type_t<T_alpha>;
+  using T_beta_ref = ref_type_t<T_beta>;
+  static constexpr const char *function = "beta_neg_binomial_rng";
+  check_consistent_sizes(function, "Number of successes parameter", r,
+                         "Prior success parameter", alpha,
+                         "Prior failure parameter", beta);
+
+  T_r_ref r_ref = r;
+  T_alpha_ref alpha_ref = alpha;
+  T_beta_ref beta_ref = beta;
+  check_positive_finite(function, "Number of successes parameter", r_ref);
+  check_positive_finite(function, "Prior success parameter", alpha_ref);
+  check_positive_finite(function, "Prior failure parameter", beta_ref);
+
+  using T_p = decltype(beta_rng(alpha_ref, beta_ref, rng));
+  T_p p = beta_rng(alpha_ref, beta_ref, rng);
+
+  scalar_seq_view<T_p> p_vec(p);
+  size_t size_p = stan::math::size(p);
+  VectorBuilder<true, double, T_p> odds_ratio_p(size_p);
+  for (size_t n = 0; n < size_p; ++n) {
+    odds_ratio_p[n] = stan::math::exp(stan::math::log(p_vec.val(n))
+                                      - stan::math::log((1 - p_vec.val(n))));
+  }
+
+  return neg_binomial_rng(r_ref, odds_ratio_p.data(), rng);
+}
+
+}  // namespace math
+}  // namespace stan
+#endif

test/unit/math/prim/prob/beta_neg_binomial_test.cpp

@@ -0,0 +1,55 @@
+#include <stan/math/prim.hpp>
+#include <test/unit/math/prim/prob/vector_rng_test_helper.hpp>
+#include <test/unit/math/prim/prob/VectorIntRNGTestRig.hpp>
+#include <boost/random/mersenne_twister.hpp>
+#include <boost/math/distributions.hpp>
+#include <gtest/gtest.h>
+#include <limits>
+#include <vector>
+
+class BetaNegBinomialTestRig : public VectorIntRNGTestRig {
+ public:
+  BetaNegBinomialTestRig()
+      : VectorIntRNGTestRig(10000, 10, {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
+                            {1.1, 3.1, 8.1}, {1, 3, 8}, {-3.0, -2.0, 0.0},
+                            {-3, -2, 0}, {3.1, 4.1, 5.1}, {3, 4, 5},
+                            {-2.1, -0.5, 0.0}, {-3, -1, 0}, {1.1, 3.1, 8.1},
+                            {1, 3, 8}, {-3.0, -2.0, 0.0}, {-3, -2, 0}) {}
+
+  template <typename T1, typename T2, typename T3, typename T_rng>
+  auto generate_samples(const T1& N, const T2& alpha, const T3& beta,
+                        T_rng& rng) const {
+    return stan::math::beta_neg_binomial_rng(N, alpha, beta, rng);
+  }
+
+  template <typename T1>
+  double pmf(int y, T1 r, double alpha, double beta) const {
+    return std::exp(stan::math::beta_neg_binomial_lpmf(y, r, alpha, beta));
+  }
+};
+
+TEST(ProbDistributionsBetaNegBinomial, errorCheck) {
+  check_dist_throws_int_first_argument(BetaNegBinomialTestRig());
+}
+
+TEST(ProbDistributionsBetaNegBinomial, distributionCheck) {
+  check_counts_int_real_real(BetaNegBinomialTestRig());
+}
+
+TEST(ProbDistributionBetaNegBinomial, error_check) {
+  boost::random::mt19937 rng;
+  EXPECT_NO_THROW(stan::math::beta_neg_binomial_rng(4, 0.6, 2.0, rng));
+
+  EXPECT_THROW(stan::math::beta_neg_binomial_rng(-4, 0.6, 2, rng),
+               std::domain_error);
+  EXPECT_THROW(stan::math::beta_neg_binomial_rng(4, -0.6, 2, rng),
+               std::domain_error);
+  EXPECT_THROW(stan::math::beta_neg_binomial_rng(4, 0.6, -2, rng),
+               std::domain_error);
+  EXPECT_THROW(stan::math::beta_neg_binomial_rng(
+                   4, stan::math::positive_infinity(), 2, rng),
+               std::domain_error);
+  EXPECT_THROW(stan::math::beta_neg_binomial_rng(
+                   4, 0.6, stan::math::positive_infinity(), rng),
+               std::domain_error);
+}