gen event = year - year_policy
tab event
replace event = -9 if event < -9
forvalues i=9(-1)1{
  gen pre`i'=(event==-`i')
}

gen current=(event==0 )

forvalues i=1(1)9{
  gen post`i'=(event==`i')
}
drop pre1
reghdfe RES pre* current post* Growth Lev ROA $control_fe, absorb(id year city_code) vce(cluster id)
///平行趋势检验折线图///
//导出回归结果（回归系数和标准误）///
coefplot,keep(pre9 pre8 pre7 pre6 pre5 pre4 pre3 pre2 current post1 post2 post3 post4 post5 post6 post7 post8 post9) levels(90) vertical lcolor(black) mcolor(black) msymbol(circle_hollow) ytitle(回归系数, size(small))  ylabel(, labsize(small) angle(horizontal) nogrid) yline(0, lwidth(vthin)lpattern(solid) lcolor(black)) xtitle(政策实施相对时间, size(small)) xlabel(,labsize(small))  graphregion(fcolor(white) lcolor(white) ifcolor(white) ilcolor(white)) ciopts(recast(rcap)) xline(10.5, lwidth(vthin) lpattern(solid)lcolor(black))