下面是我按照1对1进行匹配对照组的命令，请问需要如何改动才能进行1：3的比例选取对照组？
另外，如果对照组中出现了相同的样本应该怎么办？是否需要进行删除？

use shiyan,clear
local N=_N
mkmat code year indcd totass, mat(shiyan)

capture postclose match
postfile match code year wt match_group using mymatch,replace

forval i=1(1)`N' {
di "`i' of `N' loops completed"
drop _all
use duizhao.dta
qui keep if year==scalar(shiyan[`i',2])
qui keep if indcd==scalar(shiyan[`i',3])
gen  assetratio=abs(totass/scalar(shiyan[`i',4])-1)
qui keep if assetratio<0.2

if _N<1{
continue
}

gen distance=assetratio^2
sort distance code
qui keep if _n==1
local code1=scalar(shiyan[`i',1])
local year1=scalar(shiyan[`i',2])
local code2=code[1]
local year2=year[1]
post match (`code1') (`year1') (1) (`i')
post match (`code2') (`year2') (0) (`i')

//postfile match code year wt match_group using mymatch,replace

}
postclose match
use mymatch,clear