Stan Math Library  2.14.0
reverse mode automatic differentiation
hypergeometric_lpmf.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_PROB_HYPERGEOMETRIC_LPMF_HPP
2 #define STAN_MATH_PRIM_SCAL_PROB_HYPERGEOMETRIC_LPMF_HPP
3 
16 #include <boost/math/distributions.hpp>
17 
18 namespace stan {
19  namespace math {
20 
21  // Hypergeometric(n|N, a, b) [0 <= n <= a; 0 <= N-n <= b; 0 <= N <= a+b]
22  // n: #white balls drawn; N: #balls drawn;
23  // a: #white balls; b: #black balls
24  template <bool propto,
25  typename T_n, typename T_N,
26  typename T_a, typename T_b>
27  double
28  hypergeometric_lpmf(const T_n& n, const T_N& N,
29  const T_a& a, const T_b& b) {
30  static const char* function("hypergeometric_lpmf");
31 
32  if (!(stan::length(n)
33  && stan::length(N)
34  && stan::length(a)
35  && stan::length(b)))
36  return 0.0;
37 
38  VectorView<const T_n> n_vec(n);
39  VectorView<const T_N> N_vec(N);
40  VectorView<const T_a> a_vec(a);
41  VectorView<const T_b> b_vec(b);
42  size_t size = max_size(n, N, a, b);
43 
44  double logp(0.0);
45  check_bounded(function, "Successes variable", n, 0, a);
46  check_greater(function, "Draws parameter", N, n);
47  for (size_t i = 0; i < size; i++) {
48  check_bounded(function, "Draws parameter minus successes variable",
49  N_vec[i]-n_vec[i], 0, b_vec[i]);
50  check_bounded(function, "Draws parameter", N_vec[i], 0,
51  a_vec[i]+b_vec[i]);
52  }
53  check_consistent_sizes(function,
54  "Successes variable", n,
55  "Draws parameter", N,
56  "Successes in population parameter", a,
57  "Failures in population parameter", b);
58 
60  return 0.0;
61 
62  for (size_t i = 0; i < size; i++)
63  logp += math::binomial_coefficient_log(a_vec[i], n_vec[i])
64  + math::binomial_coefficient_log(b_vec[i], N_vec[i]-n_vec[i])
65  - math::binomial_coefficient_log(a_vec[i]+b_vec[i], N_vec[i]);
66  return logp;
67  }
68 
69  template <typename T_n,
70  typename T_N,
71  typename T_a,
72  typename T_b>
73  inline
74  double
75  hypergeometric_lpmf(const T_n& n,
76  const T_N& N,
77  const T_a& a,
78  const T_b& b) {
79  return hypergeometric_lpmf<false>(n, N, a, b);
80  }
81 
82  }
83 }
84 #endif
fvar< T > binomial_coefficient_log(const fvar< T > &x1, const fvar< T > &x2)
void check_bounded(const char *function, const char *name, const T_y &y, const T_low &low, const T_high &high)
Check if the value is between the low and high values, inclusively.
size_t length(const std::vector< T > &x)
Definition: length.hpp:10
Template metaprogram to calculate whether a summand needs to be included in a proportional (log) prob...
size_t max_size(const T1 &x1, const T2 &x2)
Definition: max_size.hpp:9
int size(const std::vector< T > &x)
Return the size of the specified standard vector.
Definition: size.hpp:17
void check_greater(const char *function, const char *name, const T_y &y, const T_low &low)
Check if y is strictly greater than low.
double hypergeometric_lpmf(const T_n &n, const T_N &N, const T_a &a, const T_b &b)
VectorView is a template expression that is constructed with a container or scalar, which it then allows to be used as an array using operator[].
Definition: VectorView.hpp:48
void check_consistent_sizes(const char *function, const char *name1, const T1 &x1, const char *name2, const T2 &x2)
Check if the dimension of x1 is consistent with x2.

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