Stolen from Radford Neal's fbm package. digamma(x) is defined as (d/dx) log Gamma(x). It is computed here using an asymptotic expansion when x>5. For x<=5, the recurrence relation digamma(x) = digamma(x+1) - 1/x is used repeatedly. See Venables & Ripley, Modern Applied Statistics with S-Plus, pp.
(double x)
source not stored for this graph (policy: none)