匹配样本时出错，求大神帮忙看看问题在哪里

forval i=1(1)`N'{
di "`i' of `N' loops completed"
drop _all
use "D:\stata13 (解压后直接打开即可）\soe.dta"
qui keep if year==scalar(private[`i',2])
qui keep if SIC12==scalar(private[`i',3])
gen asset_ratio=abs(asset/scalar(private[`i',5])-1)
qui keep if asset_ratio<0.15

if _N <1 {
continue
}
sort asset_ratio firm_id
qui keep if _n==1
local firm_id1=scalar(private[`i',1])
local year1=scalar(private[`i',2])
local firm_id2=firm_id[1]
local year2=year[1]
post match (`firm_id1')(`year1')(1)(`i')
post match (`firm_id2')(`year1')(0)(`i')

}
postclose match
报错：
unknown function ()
post:  above message corresponds to expression 1, variable firm_id
r(133);