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hypergeometric_log.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_PROB_HYPERGEOMETRIC_LOG_HPP
2 #define STAN_MATH_PRIM_SCAL_PROB_HYPERGEOMETRIC_LOG_HPP
3 
4 #include <boost/math/distributions.hpp>
19 
20 namespace stan {
21 
22  namespace math {
23 
24  // Hypergeometric(n|N, a, b) [0 <= n <= a; 0 <= N-n <= b; 0 <= N <= a+b]
25  // n: #white balls drawn; N: #balls drawn;
26  // a: #white balls; b: #black balls
27  template <bool propto,
28  typename T_n, typename T_N,
29  typename T_a, typename T_b>
30  double
31  hypergeometric_log(const T_n& n, const T_N& N,
32  const T_a& a, const T_b& b) {
33  static const char* function("stan::math::hypergeometric_log");
34 
40 
41  // check if any vectors are zero length
42  if (!(stan::length(n)
43  && stan::length(N)
44  && stan::length(a)
45  && stan::length(b)))
46  return 0.0;
47 
48 
49  VectorView<const T_n> n_vec(n);
50  VectorView<const T_N> N_vec(N);
51  VectorView<const T_a> a_vec(a);
52  VectorView<const T_b> b_vec(b);
53  size_t size = max_size(n, N, a, b);
54 
55  double logp(0.0);
56  check_bounded(function, "Successes variable", n, 0, a);
57  check_greater(function, "Draws parameter", N, n);
58  for (size_t i = 0; i < size; i++) {
59  check_bounded(function, "Draws parameter minus successes variable",
60  N_vec[i]-n_vec[i], 0, b_vec[i]);
61  check_bounded(function, "Draws parameter", N_vec[i], 0,
62  a_vec[i]+b_vec[i]);
63  }
64  check_consistent_sizes(function,
65  "Successes variable", n,
66  "Draws parameter", N,
67  "Successes in population parameter", a,
68  "Failures in population parameter", b);
69 
70  // check if no variables are involved and prop-to
72  return 0.0;
73 
74 
75  for (size_t i = 0; i < size; i++)
76  logp += math::binomial_coefficient_log(a_vec[i], n_vec[i])
77  + math::binomial_coefficient_log(b_vec[i], N_vec[i]-n_vec[i])
78  - math::binomial_coefficient_log(a_vec[i]+b_vec[i], N_vec[i]);
79  return logp;
80  }
81 
82  template <typename T_n,
83  typename T_N,
84  typename T_a,
85  typename T_b>
86  inline
87  double
88  hypergeometric_log(const T_n& n,
89  const T_N& N,
90  const T_a& a,
91  const T_b& b) {
92  return hypergeometric_log<false>(n, N, a, b);
93  }
94  }
95 }
96 #endif
fvar< T > binomial_coefficient_log(const fvar< T > &x1, const fvar< T > &x2)
double hypergeometric_log(const T_n &n, const T_N &N, const T_a &a, const T_b &b)
size_t length(const std::vector< T > &x)
Definition: length.hpp:10
bool check_bounded(const char *function, const char *name, const T_y &y, const T_low &low, const T_high &high)
Return true if the value is between the low and high values, inclusively.
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
bool check_finite(const char *function, const char *name, const T_y &y)
Return true if y is finite.
int size(const std::vector< T > &x)
Return the size of the specified standard vector.
Definition: size.hpp:17
bool check_consistent_sizes(const char *function, const char *name1, const T1 &x1, const char *name2, const T2 &x2)
Return true if the dimension of x1 is consistent with x2.
VectorView is a template metaprogram that takes its argument and allows it to be used like a vector...
Definition: VectorView.hpp:41
bool check_greater(const char *function, const char *name, const T_y &y, const T_low &low)
Return true if y is strictly greater than low.

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