cdigamma cdigamma_sub digamma polygamma trigamma

polygamma() double polygamma ( int  n, double  x  ) Polygamma function ψn(x) Purpose polygamma computes the polygamma function ψn(x), where x is not 0, -1, -2, ... ψn(x) = dnψ(x)/dxn = d(n+1)/dx(n+1) ln(Γ(x)) Returns Polygamma function ψn(x). Parameters [in] n Argument n. (n >= 0) [in] x Argument x. (x != negative integer, x != 0) Error handling If n < 0, domain error (EDOM) occurs. If x is negative integer or 0, domain error (EDOM) or range error (ERANGE) occurs. Other range error (ERANGE) may occur. Reference boost/math/special_functions