DIGAMMA Function

Returns the value of the digamma function.

Category:

Mathematical

Syntax

DIGAMMA(argument)

specifies a numeric constant, variable, or expression.

Restriction

Nonpositive integers are invalid.

The DIGAMMA function returns the ratio that is given by

\begin{matrix} Ψ (x) = Γ^{'} (x) / Γ (x) \end{matrix}

where

Γ (.)

and

Γ^{'} (.)

denote the Gamma function and its derivative, respectively. For argument>0, the DIGAMMA function is the derivative of the LGAMMA function.

The following SAS statement produces this result.

SAS Statement	Result
x=digamma(1.0);	-0.577215665