here is an example,

Q: keep the first 3 states, which have highest values of "public" in each region across years

clear
webuse productivity

gsort year region -public
bys year region : gen rank=_n

//mark those which will be deleted (delete=1)
gen delete= rank>3

l  year region state public rank delete in 1/100

不知道有rank这用法唉，Thanks，学习了~

您好，看您之前的代码collapse (max)value, by(year hangye)，发现它只能把每年每个行业的value值找出，并不能直接显示最大值所对应的行业，还需要自己后期来比较，请问如何得到每年value的最大值对应的行业名称呢？谢谢