digamma

fnreal digamma(real x)

Digamma function

The digamma function is the logarithmic derivative of the gamma function.

digamma(x) = d/dx logGamma(x)

References:

  1. Abramowitz, M., and Stegun, I. A. (1970).

Handbook of mathematical functions. Dover, New York, pages 258-259, equations 6.3.6 and 6.3.18.