cd "C:\Users\xzyd00\Desktop\usyd\master\2019semester1\thesis\data file\2012-2018 price data\BPE0331 30min price"
use "2012_bpe0331.csv.dta",clear
drop if _n>=1
save "combined_bpe",replace

forvalues loopnum = 2012/2018 {
di "loopnum is: ",`loopnum'
append using "`loopnum'_bpe0331.csv.dta"
}
为什么我这样无法得到合并的文件？这个combined 文件只有第一栏的变量