在采取模型计算操纵性应计盈余指标时，在使用循环函数是出现无效指令，这是什么原因造成的，想知道是不是应该把空缺值删掉？gen EXBI=yingyeshouru-yingyechengben
gen cfo=jingyingxianjinjin-jingyingxianjinchu

gen year1=year(acc)
xtset stkcd year1
gen Acc=(EXBI-cfo)/L.zongzichan
gen invA=1/L.zongzichan
gen Dsale=D.yingyeshouru/L.zongzichan
gen Dar=yingshouzhangkuan/L.zongzichan
gen Ds_Dar=Dsale-Dar
gen Ppe=gudingzichan/L.zongzichan
egen ind_year=group(ind year1),label lname(ind_year)


gen Dacc=.
        forvalues i=1/$N{
                qui reg Acc invA Ds_Dar Ppe if (ind_year==`i'),nocons
                qui predict e if e(sample),res
                qui replace Dacc =e if e(sample)
                drop e
        }


  dataex  Acc invA Ds_Dar Ppe  in 1/100
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Listed 100 out of 2392 observations

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