Stan Math Library  2.12.0
reverse mode automatic differentiation
log_rising_factorial.hpp
Go to the documentation of this file.
1 #ifndef STAN_MATH_FWD_SCAL_FUN_LOG_RISING_FACTORIAL_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_LOG_RISING_FACTORIAL_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 
7 #include <boost/math/special_functions/digamma.hpp>
8 
9 namespace stan {
10  namespace math {
11 
12  template<typename T>
13  inline
14  fvar<T>
15  log_rising_factorial(const fvar<T>& x, const fvar<T>& n) {
17 
19  (digamma(x.val_ + n.val_) * (x.d_ + n.d_)
20  - digamma(x.val_) * x.d_));
21  }
22 
23  template<typename T>
24  inline
25  fvar<T>
26  log_rising_factorial(const fvar<T>& x, const double n) {
28 
29  return fvar<T>(log_rising_factorial(x.val_, n),
30  (digamma(x.val_ + n) - digamma(x.val_)) * x.d_);
31  }
32 
33  template<typename T>
34  inline
35  fvar<T>
36  log_rising_factorial(const double x, const fvar<T>& n) {
38 
39  return fvar<T>(log_rising_factorial(x, n.val_),
40  (digamma(x + n.val_) * n.d_));
41  }
42  }
43 }
44 #endif
fvar< T > log_rising_factorial(const fvar< T > &x, const fvar< T > &n)
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:15

     [ Stan Home Page ] © 2011–2016, Stan Development Team.