beta_neg_binomial_rng.hpp

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#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 {
 
template <typename T_r, typename T_alpha, typename T_beta, typename RNG>
inline auto 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)) - log1m(p_vec.val(n)));
  }
 
  return neg_binomial_rng(r_ref, odds_ratio_p.data(), rng);
}
 
}  // namespace math
}  // namespace stan
#endif