if命令求助

请各位stata的老师帮忙看一下，如何实现下面的需求，谢谢了。
如果时间year在2013年的时候，对应的变量time等于1，则将year<=2013年的时候，变量policy =year -2013

if time == 1 & year <= 2013 {
    replace policy = year - 2013
}

2229990 发表于 2023-12-14 11:43
if time == 1 & year

您好，我运行了以后，变量值没有任何变化

gen policy = .replace policy = year - 2013 if time == 1 & year <= 2013

题主应该是想先把13年时time=1的个体先筛选出来？我假设你代表个体的变量是id：
gen t1 = ( time == 1 & year == 2013 )
bys id: gen want = sum(t1)
gen policy = year - 2013 if ( want == 1 & year <= 2013)
drop t1 want

gen time = 0
gen policy = .

foreach year in 2013/. {
    if `year\' == 2013 {
        gen time = 1
    } else {
        gen policy = `year\' - 2013
    }
}