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chi_square_cdf_log.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_PROB_CHI_SQUARE_CDF_LOG_HPP
2 #define STAN_MATH_PRIM_SCAL_PROB_CHI_SQUARE_CDF_LOG_HPP
3
4 #include <stan/math/prim/scal/meta/OperandsAndPartials.hpp>
5 #include <stan/math/prim/scal/err/check_consistent_sizes.hpp>
6 #include <stan/math/prim/scal/err/check_nonnegative.hpp>
7 #include <stan/math/prim/scal/err/check_not_nan.hpp>
8 #include <stan/math/prim/scal/err/check_positive_finite.hpp>
9 #include <stan/math/prim/scal/fun/constants.hpp>
10 #include <stan/math/prim/scal/fun/multiply_log.hpp>
11 #include <stan/math/prim/scal/fun/value_of.hpp>
12 #include <stan/math/prim/scal/fun/gamma_p.hpp>
13 #include <stan/math/prim/scal/fun/digamma.hpp>
14 #include <stan/math/prim/scal/meta/VectorBuilder.hpp>
15 #include <stan/math/prim/scal/fun/grad_reg_inc_gamma.hpp>
16 #include <stan/math/prim/scal/meta/include_summand.hpp>
17 #include <boost/random/chi_squared_distribution.hpp>
18 #include <boost/random/variate_generator.hpp>
19 #include <cmath>
20 #include <limits>
21
22 namespace stan {
23
24 namespace math {
25
26 template <typename T_y, typename T_dof>
27 typename return_type<T_y, T_dof>::type
28 chi_square_cdf_log(const T_y& y, const T_dof& nu) {
29 static const char* function("stan::math::chi_square_cdf_log");
30 typedef typename stan::partials_return_type<T_y, T_dof>::type
31 T_partials_return;
32
33 using stan::math::check_positive_finite;
34 using stan::math::check_nonnegative;
35 using stan::math::check_not_nan;
36 using stan::math::check_consistent_sizes;
37 using stan::math::value_of;
38
39 T_partials_return cdf_log(0.0);
40
41 // Size checks
42 if (!(stan::length(y) && stan::length(nu)))
43 return cdf_log;
44
45 check_not_nan(function, "Random variable", y);
46 check_nonnegative(function, "Random variable", y);
47 check_positive_finite(function, "Degrees of freedom parameter", nu);
48 check_consistent_sizes(function,
49 "Random variable", y,
50 "Degrees of freedom parameter", nu);
51
52 // Wrap arguments in vectors
53 VectorView<const T_y> y_vec(y);
54 VectorView<const T_dof> nu_vec(nu);
55 size_t N = max_size(y, nu);
56
57 OperandsAndPartials<T_y, T_dof>
58 operands_and_partials(y, nu);
59
60 // Explicit return for extreme values
61 // The gradients are technically ill-defined, but treated as zero
62 for (size_t i = 0; i < stan::length(y); i++) {
63 if (value_of(y_vec[i]) == 0)
64 return operands_and_partials.to_var(stan::math::negative_infinity(),
65 y, nu);
66 }
67
68 // Compute cdf_log and its gradients
69 using stan::math::gamma_p;
70 using stan::math::digamma;
71 using boost::math::tgamma;
72 using std::exp;
73 using std::pow;
74 using std::log;
75 using std::exp;
76
77 // Cache a few expensive function calls if nu is a parameter
78 VectorBuilder<!is_constant_struct<T_dof>::value,
79 T_partials_return, T_dof> gamma_vec(stan::length(nu));
80 VectorBuilder<!is_constant_struct<T_dof>::value,
81 T_partials_return, T_dof> digamma_vec(stan::length(nu));
82
83 if (!is_constant_struct<T_dof>::value) {
84 for (size_t i = 0; i < stan::length(nu); i++) {
85 const T_partials_return alpha_dbl = value_of(nu_vec[i]) * 0.5;
86 gamma_vec[i] = tgamma(alpha_dbl);
87 digamma_vec[i] = digamma(alpha_dbl);
88 }
89 }
90
91 // Compute vectorized cdf_log and gradient
92 for (size_t n = 0; n < N; n++) {
93 // Explicit results for extreme values
94 // The gradients are technically ill-defined, but treated as zero
95 if (value_of(y_vec[n]) == std::numeric_limits<double>::infinity())
96 return operands_and_partials.to_var(0.0, y, nu);
97
98 // Pull out values
99 const T_partials_return y_dbl = value_of(y_vec[n]);
100 const T_partials_return alpha_dbl = value_of(nu_vec[n]) * 0.5;
101 const T_partials_return beta_dbl = 0.5;
102
103 // Compute
104 const T_partials_return Pn = gamma_p(alpha_dbl, beta_dbl * y_dbl);
105
106 cdf_log += log(Pn);
107
108 if (!is_constant_struct<T_y>::value)
109 operands_and_partials.d_x1[n] += beta_dbl * exp(-beta_dbl * y_dbl)
110 * pow(beta_dbl * y_dbl, alpha_dbl-1) / tgamma(alpha_dbl) / Pn;
111 if (!is_constant_struct<T_dof>::value)
112 operands_and_partials.d_x2[n]
113 -= 0.5 * stan::math::grad_reg_inc_gamma(alpha_dbl, beta_dbl
114 * y_dbl, gamma_vec[n],
115 digamma_vec[n]) / Pn;
116 }
117
118 return operands_and_partials.to_var(cdf_log, y, nu);
119 }
120
121 }
122 }
123 #endif
check_not_nan.hpp
stan::math::check_not_nan
bool check_not_nan(const char *function, const char *name, const T_y &y)
Return true if y is not NaN.
Definition: check_not_nan.hpp:63
check_positive_finite.hpp
stan::math::value_of
T value_of(const fvar< T > &v)
Return the value of the specified variable.
Definition: value_of.hpp:16
digamma.hpp
stan::math::log
fvar< T > log(const fvar< T > &x)
Definition: log.hpp:15
stan::length
size_t length(const std::vector< T > &x)
Definition: length.hpp:10
stan::math::OperandsAndPartials::to_var
T_return_type to_var(T_partials_return logp, const T1 &x1=0, const T2 &x2=0, const T3 &x3=0, const T4 &x4=0, const T5 &x5=0, const T6 &x6=0)
Definition: OperandsAndPartials.hpp:322
stan::math::grad_reg_inc_gamma
T grad_reg_inc_gamma(T a, T z, T g, T dig, T precision=1e-6)
Definition: grad_reg_inc_gamma.hpp:15
include_summand.hpp
multiply_log.hpp
stan::math::OperandsAndPartials::d_x1
VectorView< T_partials_return, is_vector< T1 >::value, is_constant_struct< T1 >::value > d_x1
Definition: OperandsAndPartials.hpp:253
check_nonnegative.hpp
stan::is_constant_struct
Metaprogram to determine if a type has a base scalar type that can be assigned to type double...
Definition: is_constant_struct.hpp:16
stan::math::exp
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
stan::math::OperandsAndPartials
A variable implementation that stores operands and derivatives with respect to the variable...
Definition: OperandsAndPartials.hpp:238
stan::math::chi_square_cdf_log
return_type< T_y, T_dof >::type chi_square_cdf_log(const T_y &y, const T_dof &nu)
Definition: chi_square_cdf_log.hpp:28
OperandsAndPartials.hpp
stan::max_size
size_t max_size(const T1 &x1, const T2 &x2)
Definition: max_size.hpp:9
VectorBuilder.hpp
stan::math::gamma_p
fvar< T > gamma_p(const fvar< T > &x1, const fvar< T > &x2)
Definition: gamma_p.hpp:15
gamma_p.hpp
grad_reg_inc_gamma.hpp
stan::VectorBuilder
Definition: VectorBuilder.hpp:61
constants.hpp
stan::math::check_consistent_sizes
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.
Definition: check_consistent_sizes.hpp:31
stan::math::OperandsAndPartials::d_x2
VectorView< T_partials_return, is_vector< T2 >::value, is_constant_struct< T2 >::value > d_x2
Definition: OperandsAndPartials.hpp:256
stan::math::pow
fvar< T > pow(const fvar< T > &x1, const fvar< T > &x2)
Definition: pow.hpp:18
stan::math::check_nonnegative
bool check_nonnegative(const char *function, const char *name, const T_y &y)
Return true if y is non-negative.
Definition: check_nonnegative.hpp:66
value_of.hpp
stan::math::tgamma
fvar< T > tgamma(const fvar< T > &x)
Definition: tgamma.hpp:15
stan::VectorView
VectorView is a template metaprogram that takes its argument and allows it to be used like a vector...
Definition: VectorView.hpp:41
stan::partials_return_type::type
boost::math::tools::promote_args< typename partials_type< typename scalar_type< T1 >::type >::type, typename partials_type< typename scalar_type< T2 >::type >::type, typename partials_type< typename scalar_type< T3 >::type >::type, typename partials_type< typename scalar_type< T4 >::type >::type, typename partials_type< typename scalar_type< T5 >::type >::type, typename partials_type< typename scalar_type< T6 >::type >::type >::type type
Definition: partials_return_type.hpp:26
check_consistent_sizes.hpp
stan::math::check_positive_finite
bool check_positive_finite(const char *function, const char *name, const T_y &y)
Return true if y is positive and finite.
Definition: check_positive_finite.hpp:28
stan::math::negative_infinity
double negative_infinity()
Return negative infinity.
Definition: constants.hpp:132
stan::math::digamma
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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