Cdigamma Digamma Polygamma Trigamma

Cdigamma() Function Cdigamma ( Z As  Complex, Optional Info As  Long  ) Digamma (or psi) function ψ(z) (complex argument) Purpose This routine computes the digamma (or psi) function at a complex number z, where z is not 0, -1, -2, ... ψ(z) = d/dz ln(Γ(z)) = Γ'(z)/Γ(z) Returns Complex Digamma (or psi) function ψ(z). Parameters [in] Z Argument z. (Z <> 0 and Z <> a negative integer) [out] Info (Optional) = 0: Successful exit. = -1: The argument Z had an illegal value. (Z = 0 or a negative integer) = 1: Floating point range error.