以下是我的命令的关键部分
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

删掉了一些观测值不够的样本
drop if count_event_obs < 5
drop if count_est_obs < 30

drop count_event_obs
drop count_est_obs

set more off

gen predicted_return=.
egen id=group(group_id)  
forvalues i=1/118{
        list 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
}

问题1：执行到这条以后显示no observations，问题可能出在哪里？
问题2：我的研究样本一共118个，前面删掉了观察值不够的样本23个，理应还有95个，但最后输出excel表中只有60多个样本是怎么回事呢？