Stata：计算一段时间内的平均值

Question

我需要对20个句点进行以下计算，并且与forval命令不相符，因为我正在学习如何处理Stata。

这是我需要重复20个时期的内容：

egen avg1 = mean(price1) if  Period == 1
egen avg2 = mean(price2) if  Period == 1
gen AVG = avg1+avg2
gen AVG_t1=AVG/2
drop avg1 avg2 AVG

并尝试使用forval解决问题：

    sort Period
local j = Period
forval j = 1/20 { 
     egen avg1 = mean(price1) if  Period == `j' 
     egen avg2 = mean(price2) if  Period == `j'
     gen AVG = avg1+avg2 if  Period == `j' 
     gen AVG_t`j'=AVG/2 if  Period == `j'  
     drop avg1 avg2 AVG if Period == `j' 
} 

Answer 1

研究egen的帮助，看它比你想象的更灵活。

 egen avg1 = mean(price1), by(Period) 
 egen avg2 = mean(price2), by(Period) 
 gen AVG_t1 = (avg1 + avg2) / 2 

您的循环将失败，因为第二次avg1已经存在。记录的内容是

 bysort Period: egen avg1 = mean(price1) 
 by Period: egen avg2 = mean(price2) 

但上面的语法可行。