*!version 2.0.0  10Jun1998 Joseph Hilbe  STB-45 dm60
* trigamma function
* EX: trigamma (var), g(newvar)
program define trigamma
  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'+.002) + 16*lngamma(`1'+.001)
               -30*lngamma(`1')   + 16*lngamma(`1'-.001)
               -lngamma(`1'-.002) ) / .000012 `if' `in' ;
  #delimit cr
end