program define permt2
 version 4.0
 local grp "`1'"
 local x "`2'"
 tempvar sum
 quietly {
 if "$S_1"=="first" {
 gen double `sum'=sum(`x')
 scalar _TOTAL = `sum'[_N]
 drop `sum'
 summarize `grp'
 scalar _GROUP1 = _result(5)
 count if `grp'== _GROUP1
 scalar _TOTAL = (_result(1)/_N)*_TOTAL
 }
 gen double `sum'=sum((`grp'==_GROUP1)*`x')
 global S_1 = `sum'[_N] - _TOTAL
 }
 end