求助，导师问我为什么基期这里灰色的线相交了，没有平行。请问该怎么解释哇，那个代码跑出来就是这样的，别人的样例也是这样相交的<br>
以下是代码<br>
**以-1为基期<br>
*声明面板数据<br>
encode ID, gen(Code)<br>
xtset Code Year<br>
*生成dist变量<br>
gen dist = Year-2012
forvalues i = 3(-1)1 { <br>
    gen pre_`i' = (dist == -`i') <br>
    }<br>
forvalues i = 0(1)5 { <br>
    gen post_`i' = (dist == `i') <br>
    }<br>
replace pre_1 = 0<br>
reghdfe GTI pre_* post_*, absorb(Code) vce(cluster Code)
parmest, format(estimate min95 max95 %8.3f p %8.3f)  saving("temp1.dta", replace)
use "temp1.dta", clear<br>
keep if ustrregexm(parm, "pre|post")<br>
gen num = _n<br>
gen minus = num if ustrregexm(parm, "o.pre_1")<br>
fillmissing minus<br>
gen id = num - minus - 1<br>
egen average = mean(estimate) if id < -1<br>
fillmissing average
replace estimate = estimate - average<br>
gen ul = estimate + stderr * 1.96<br>
gen ll = estimate - stderr * 1.96<br>
for var estimate ul ll: replace X = 0 if mi(t)
#delimit ;<br>
two (scatter estimate id, c(l) color(black) msize(small)) (scatter ul id, c(l) m(none) color(gs10) lp(dash)) (scatter ll id, c(l) m(none) color(gs10) lp(dash)),xtitle("") yline(0) xline(-1, lp(dash) lc(black)) xlabel(, grid) ylabel(, grid format(%4.2f)) legend(off) graphregion(color(white)) plotregion(lcolor(black))<br>
#delimit cr<br>
graph export "figure4.png", width(1000) replace