*!version 1.2.0  : 10Jun1998  Joseph Hilbe     STB-45 dm60
* digamma function : derivative of lngamma function
* EX: digamma (var), g(newvar)
program define digamma
  version 5.0
  local varlist "req ex min(1) max(1)"
  local options "Generate(string)"
  local if "opt"
  local in "opt"
  parse "`*'"
  parse "`varlist'", parse(" ")
  confirm new var `generat'
  #delimit ;
  qui gen `generat' = (lngamma(`1'+.0001)-
     lngamma(`1'-.0001))/.0002 `if' `in' ;
  #delimit cr
end