digamma.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_DIGAMMA_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_DIGAMMA_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 
8 
9 namespace stan {
10 namespace math {
11 
12 /**
13  * Return the derivative of the log gamma function at the
14  * specified argument.
15  *
16  * @tparam T scalar type of autodiff variable
17  * @param[in] x argument
18  * @return derivative of the log gamma function at the specified
19  * argument
20  */
21 template <typename T>
22 inline fvar<T> digamma(const fvar<T>& x) {
23  return fvar<T>(digamma(x.val_), x.d_ * trigamma(x.val_));
24 }
25 } // namespace math
26 } // namespace stan
27 #endif
fvar< T > trigamma(const fvar< T > &u)
Definition: trigamma.hpp:21
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:22