我在stata里编写程序如下：
clear
program NO_oMI, rclass
drop _all
set obs 100
gen ui= rnormal(0,2)
gen vi= rnormal(0,3)
gen xi = rnormal(100,10)
for i <= 100{
gen yi = 150 - 2*xi + ui
i = i + 1
t = yi
gen xi = -20 + 4*t + vi
end
qui reg yi xi
return scalar bhat = _b[x]
end

simulate best1 = r(bhat), seed(001) reps(10000) nodots: NO_oMI
summarize(best1)

但是stata里运行不了   错误原因显示为yi那里我好想没写明白
但是我不知道怎么改了    求教一下