*-行业重新编码 1,2,3 ……
cap drop sic123
egen sic123 = group(sic2 year), label lname(sic_year)
qui sum sic123
global N = r(max)
*-分行业, 分年度回归分析
dropvars DACC e
gen DACC = .
forvalues i = 1/$N{
qui reg acc invA DS_DAR PPE if (sic123==`i')
qui predict e if e(sample), res
qui replace DACC = e if e(sample)
drop e
}