1 #ifndef STAN_MATH_PRIM_SCAL_PROB_CHI_SQUARE_LPDF_HPP 2 #define STAN_MATH_PRIM_SCAL_PROB_CHI_SQUARE_LPDF_HPP 38 template <
bool propto,
typename T_y,
typename T_dof>
41 static const char*
function =
"chi_square_lpdf";
49 "Degrees of freedom parameter", nu);
53 T_partials_return logp(0);
59 for (
size_t n = 0; n <
length(y); n++)
71 for (
size_t i = 0; i <
length(y); i++)
77 for (
size_t i = 0; i <
length(y); i++)
82 lgamma_half_nu(
length(nu));
84 digamma_half_nu_over_two(
length(nu));
86 for (
size_t i = 0; i <
length(nu); i++) {
87 T_partials_return half_nu = 0.5 *
value_of(nu_vec[i]);
89 lgamma_half_nu[i] =
lgamma(half_nu);
91 digamma_half_nu_over_two[i] =
digamma(half_nu) * 0.5;
96 for (
size_t n = 0; n < N; n++) {
97 const T_partials_return y_dbl =
value_of(y_vec[n]);
98 const T_partials_return half_y = 0.5 * y_dbl;
99 const T_partials_return nu_dbl =
value_of(nu_vec[n]);
100 const T_partials_return half_nu = 0.5 * nu_dbl;
104 logp += (half_nu - 1.0) * log_y[n];
109 ops_partials.
edge1_.partials_[n] += (half_nu - 1.0) * inv_y[n] - 0.5;
113 - digamma_half_nu_over_two[n]
117 return ops_partials.
build(logp);
120 template <
typename T_y,
typename T_dof>
123 return chi_square_lpdf<false>(y, nu);
return_type< T_y, T_dof >::type chi_square_lpdf(const T_y &y, const T_dof &nu)
The log of a chi-squared density for y with the specified degrees of freedom parameter.
boost::math::tools::promote_args< double, typename partials_type< typename scalar_type< T >::type >::type, typename partials_return_type< T_pack... >::type >::type type
fvar< T > lgamma(const fvar< T > &x)
Return the natural logarithm of the gamma function applied to the specified argument.
T value_of(const fvar< T > &v)
Return the value of the specified variable.
Extends std::true_type when instantiated with zero or more template parameters, all of which extend t...
fvar< T > log(const fvar< T > &x)
scalar_seq_view provides a uniform sequence-like wrapper around either a scalar or a sequence of scal...
This template builds partial derivatives with respect to a set of operands.
size_t length(const std::vector< T > &x)
Returns the length of the provided std::vector.
bool size_zero(T &x)
Returns 1 if input is of length 0, returns 0 otherwise.
Template metaprogram to calculate whether a summand needs to be included in a proportional (log) prob...
void check_nonnegative(const char *function, const char *name, const T_y &y)
Check if y is non-negative.
void check_positive_finite(const char *function, const char *name, const T_y &y)
Check if y is positive and finite.
boost::math::tools::promote_args< double, typename scalar_type< T >::type, typename return_type< Types_pack... >::type >::type type
void check_not_nan(const char *function, const char *name, const T_y &y)
Check if y is not NaN.
size_t max_size(const T1 &x1, const T2 &x2)
T_return_type build(double value)
Build the node to be stored on the autodiff graph.
VectorBuilder allocates type T1 values to be used as intermediate values.
internal::ops_partials_edge< double, Op2 > edge2_
const double NEG_LOG_TWO_OVER_TWO
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.
internal::ops_partials_edge< double, Op1 > edge1_
fvar< T > digamma(const fvar< T > &x)
Return the derivative of the log gamma function at the specified argument.