*! version 1.2.0   13 September 1993   RG       STB-17: sg21
program define equip
    version 3.1
* enter control group first: p n p n, delta() sdelta2()]
* enter control group first: p n pbase, delta() sdelta2()]
    local options "Delta(string) SDelta(string) BY(string)"
    local exp "opt noprefix"
    local if "opt"
    local in "opt"
    local varlist "req ex max(1)"
    parse "`*'"
    cap confirm number `exp'
    if _rc==0 {
         if "`by'"!="" {
              di in red "may not use by() in this situation"
              exit 198
         }
         qui su `varlist' `if' `in'
         local n1=_result(1)
         local u1=_result(3)
         if "`delta'"=="" { local delta=.2*`exp' }
         if "`delta'"!="" {
              if "`sdelta'"=="" {
                   local sdelta `delta'
              }
         }
         equipi `u1' `n1' `exp', d("`delta'") sd("`sdelta'")
         exit
    }
    cap confirm var `exp'
    if _rc==0 {
         if "`by'"!="" {
              di in red "may not combine second variable with by()"
              exit 198
         }
         quietly sum `varlist' `if' `in'
         local n1 = _result(1)
         local u1 = _result(3)
         quietly sum `exp' `if' `in'
         local n2 = _result(1)
         local u2 = _result(3)
         if "`delta'"!="" {
              if "`sdelta'"=="" {
                   local sdelta `delta'
              }
              equipi `u1' `n1' `u2' `n2', d("`delta'") sd("`sdelta'")
         }
         else { equipi `u1' `n1' `u2' `n2' }
         exit
    }
    if "`by'"!="" {
         confirm var `by'
         quietly tab `by' `if' `in'
         if _result(2)!=2 {
              di in red "`by' takes on " _result(2) " values, not 2"
              exit 450
         }
         tempvar M TOUSE
         quietly gen byte `TOUSE' = 1 `if' `in'
         sort `by' `TOUSE'
         quietly by `by' `TOUSE': gen byte `M'=cond(_n==1,1,.) if `TOUSE'==1
         sort `M' `by'
         quietly sum `varlist' if `by'==`by'[1] & `TOUSE'==1
         local n1 = _result(1)
         local u1 = _result(3)
         quietly sum `varlist' if `by'==`by'[2] & `TOUSE'==1
         local n2 = _result(1)
         local u2 = _result(3)
         if "`delta'"!="" {
              if "`sdelta'"=="" {
                   local sdelta `delta'
              }
              equipi `u1' `n1' `u2' `n2', d("`delta'") sd("`sdelta'")
         }
         else { equipi `u1' `n1' `u2' `n2' }
    }
end