WDigamma WPolygamma

WDigamma() Function WDigamma ( X As  Double ) Digamma (or psi) function ψ(x) Purpose WDigamma computes the psi (or digamma) function at x, where x is not 0, -1, -2, ... ψ(x) = d/dx ln(Γ(x)) = Γ'(x)/Γ(x) Returns Digamma (or psi) function ψ(x). Parameters [in] X Argument x. (X <> 0 and X <> an negative integer) Reference boost/math/special_functions