beta_proportion_rng.hpp

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#ifndef STAN_MATH_PRIM_PROB_BETA_PROPORTION_RNG_HPP
#define STAN_MATH_PRIM_PROB_BETA_PROPORTION_RNG_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/max_size.hpp>
#include <stan/math/prim/fun/size_zero.hpp>
#include <stan/math/prim/fun/scalar_seq_view.hpp>
#include <stan/math/prim/fun/to_ref.hpp>
#include <boost/random/variate_generator.hpp>
 
namespace stan {
namespace math {
 
template <typename T_loc, typename T_prec, class RNG>
inline typename VectorBuilder<true, double, T_loc, T_prec>::type
beta_proportion_rng(const T_loc &mu, const T_prec &kappa, RNG &rng) {
  using T_mu_ref = ref_type_t<T_loc>;
  using T_kappa_ref = ref_type_t<T_prec>;
  static constexpr const char *function = "beta_proportion_rng";
  check_consistent_sizes(function, "Location parameter", mu,
                         "Precision parameter", kappa);
 
  if (size_zero(mu, kappa)) {
    return {};
  }
 
  T_mu_ref mu_ref = mu;
  T_kappa_ref kappa_ref = kappa;
  check_positive(function, "Location parameter", mu_ref);
  check_less(function, "Location parameter", mu_ref, 1.0);
  check_positive_finite(function, "Precision parameter", kappa_ref);
 
  scalar_seq_view<T_mu_ref> mu_vec(mu_ref);
  scalar_seq_view<T_kappa_ref> kappa_vec(kappa_ref);
  size_t N = max_size(mu, kappa);
  VectorBuilder<true, double, T_loc, T_prec> output(N);
 
  for (size_t n = 0; n < N; ++n) {
    double alpha = mu_vec[n] * kappa_vec[n];
    double beta = kappa_vec[n] - alpha;
    output[n] = beta_rng(alpha, beta, rng);
  }
 
  return output.data();
}
 
}  // namespace math
}  // namespace stan
#endif