Dear Allin and Jack,
I think there is an error in the definition of the digamma function in Gretl Command Reference.
Now we have:
<tex>
\psi(x) = d\Gamma(x)/dx
<\tex>
And I think it should be:
<tex>
\psi(x) = d\Gamma'(x)/dx
<\tex>
Um abraço,
Henrique Andrade