*! created 08/11/93 :                   ssa6: STB-22
program define slice
	version 3.0 
	local varlist "req ex min(1) max(1)"
	local if "opt"
	local in "opt"
	local options "Interval(string) TVid(string) SAVing(string) START(string) GENerate(string) NOLABel"

	parse "`*'"
	parse "`varlist'", parse(" ")
	tempvar beg obs end n Tinit rec
	tempfile TEMP

	quietly { 
		if ("`if'`in'"!="") {
			tempvar touse
			gen `touse'=0
			replace `touse'=1 `if' `in'
		}
		else	local touse 1
	}

* keep in memory the original file name
	local sfn "$S_FN"
	quietly save `TEMP', replace

	capture { 	/* Intercept break key	*/
		if "`tvid'"!="" { 
			confirm var `tvid' 
			sort `tvid' `1'
		}
		else {
			noi di in red "Time varying identifier not specified"
			err 198
			}

		if "`start'"!="" { 
			confirm var `start' 
			gen int `beg'=`start'
		}
		else { by `tvid': gen int `beg'=cond(_n==1 | `1'[_n-1]==.,0,`1'[_n-1]) if `1'!=. } 

		if "`generate'"!="" { 
			confirm new variable `generate'
			gen byte `generate'=0 if `1'!=. & `touse'==1 
		}
		else {
			noi di in red "generate(new_var) is not optional"
			err 198
			}

		local time "`1'"
		gen int `end'=`1'
		local n 1
		local Tinit=_N
		local rec=_N

		if "`interval'"=="" {
			noi di in red "interval() is not optional"
			err 198
		}
		else { 
			if "`interval'"=="w" { local interval "0 7 15 30 60 90 180 360 540 720" }
			parse "`interval'", parse(", ")
			if "`2'"=="" { 
				confirm integer number `1'
				if `1'<=0 | `1'== . { 
					di in red "interval() invalid"
					exit 198
				}
				local last=`1'
				local int "0"
				quietly summ `end', detail
				while `last'<_result(6) {
					local int "`int' `last'"
					local last=`last'+`1'
				}
				parse "`int'", parse(" ")
			} /* end if */
			local last -1
			by `tvid': gen int `obs'=_n
			while "`1'"!="" {
			if "`1'"!="," { 
				confirm integer number `1'
				if `1'<=`last' { 
					di in red "intervals must be ascending"
					exit 198
				}
				by `tvid': replace `obs'=_n
				expand =2 if `beg'<`end' & `beg'<`1' & `end'>`1' & `end'!=. & `touse'==1, clear
				sort `tvid' `obs'
				replace `end'=`1' if `beg'<`end' & `beg'<`1' & `end'>`1'-1 & `end'==`end'[_n+1] & `tvid'==`tvid'[_n+1] & `obs'==`obs'[_n+1] & `end'!=. & `touse'==1
				replace `beg'=`1' if `beg'<`end' & `beg'<`1' & `end'>`1' & `beg'==`beg'[_n-1] & `tvid'==`tvid'[_n-1] & `obs'==`obs'[_n-1] & `end'!=. & `touse'==1
				replace `generate'=`n' if `beg'>=`1' & `end'!=. & `touse'==1
				if `n'==1 { noi di "   -" _c }
				noi di "`1'    + " _N-`rec' _n "[`1'-" _c
				local rec=_N
				local n =`n'+1
				local last `1'
				local list "`list' `1'"
			} /* end if */
			macro shift
			}
			if "`nolabel'"=="" {
				parse "`list'", parse(", ")
				label def `generate' 0 "   -`1'" 1 "[`1'-`2'" 2 "[`2'-`3'" 3 "[`3'-`4'" 4 "[`4'-`5'" 5 "[`5'-`6'" 6 "[`6'-`7'" 7 "[`7'-`8'" 8 "[`8'-`9'" 9 "[`9'-`10'" 10 "[`10'-`11'" 11 "[`11'-`12'" 12 "[`12'-`13'" 13 "[`13'-`14'" 14 "[`14'-`15'" 15 "[`15'-`16'" 16 "[`16'-`17'" 17 "[`17'-`18'" 18 "[`18'-`19'" 19 "[`19'-`20'" 20 "[`20'-`21'"
			}
		} /* end if */
		lab var `generate' "Time period `generate'"
		lab val `generate' `generate' 
		noi di "     --------"
		noi di "           " _N-`Tinit' " records added to " `Tinit' 
		if "`start'"!="" { 
			replace `start'=`beg' if `touse'==1
		}
		replace `time'=`end' if `touse'==1
		sort `tvid' `time'
	} /* end capture */
	local rc = _rc 
	if `rc'==0  { 
		capture {
			save `saving'
			}
		if `rc'!=0 { 
			quietly use `TEMP', clear
			mac def S_FN "`sfn'"
		}
	}
	else {
		quietly use `TEMP', clear
		mac def S_FN "`sfn'"
	}
	erase `TEMP'
	error `rc'
end

* slice v638, tvid(no) start(v603) interval(75,78,81,84,87,90) saving(new) gen(periode)