FNDigammareturns the value of the digamma function (sometimes called thepsifunction) ofx,ψ(x). The value ofψ(x) approaches ± asxapproaches a negative integer value or zero.
Errors
FNDigammacauses an HTBasic error if its argument is not of type REAL or if the magnitude ofψ(x) exceeds MAXREAL, the largest number representable.