本人在用stata做事件研究法，用样本数据和代码实验，感觉代码的循环部分有错误，不能做下去，请大家帮我看看循环部分有什么问题，应该怎样改
use D:\mystata\eventdates
sort company_id
by company_id: gen eventcount=_N
by company_id: keep if _n==1
keep company_id eventcount
save D:\mystata\eventcount

use D:\mystata\stockdata, clear
sort company_id
merge company_id using D:\mystata\eventcount
tab _merge
keep if _merge==3
drop _merge
expand eventcount
drop eventcount
sort company_id date
by company_id date: gen set=_n
sort company_id set
save D:\mystata\stockdata2
use D:\mystata\eventdates, clear
sort company_id
by company_id: gen set=_n
sort company_id set
save D:\mystata\eventdates2
use D:\mystata\stockdata2, clear
merge company_id set using D:\mystata\eventdates2
tab _merge       
list company_id if _merge==2
keep if _merge==3
drop _merge
egen group_id = group(company_id set)
/*group()是把group中的变量看作n维数组，按照取值的不同组合进行编号*/





sort company_id date
by company_id: gen datenum=_n
by company_id: gen target=datenum if date==event_date
egen td=min(target), by(company_id)
drop target
gen dif=datenum-td

by company_id: gen event_window=1 if dif>=-2 & dif<=2
egen count_event_obs=count(event_window), by(company_id)
by company_id: gen estimation_window=1 if dif<-30 & dif>=-60
egen count_est_obs=count(estimation_window), by(company_id)
replace event_window=0 if event_window==.
replace estimation_window=0 if estimation_window==.

tab company_id if count_event_obs<5
tab company_id if count_est_obs<30
drop if count_event_obs < 5
drop if count_est_obs < 30

set more off

gen predicted_return=.
egen id=group(company_id)
forvalues i=1(1)N {
        1 id company_id if id==`i'&dif==0
        reg ret market_return if id==`i'& estimation_window==1
        predict p if id==`i'
        replace predicted_return=p if id==`i'&event_window==1
    drop p
}  
sort id date
gen abnormal_return=ret-predicted_return if event_window==1
by id: egen cumulative_abnormal_return = sum(abnormal_return)
sort id date
by id: egen ar_sd = sd(abnormal_return)
gen test =(1/sqrt(number of days in event window)) * ( cumulative_abnormal_return /ar_sd)
list company_id cumulative_abnormal_return test if dif==0

outsheet  using D:/mystata/company_id event_date cumulative_abnormal_return test using stats.csv if dif==0, comma names