STATA只提取某一列的某几类数据,但是数据是字母+数字的组合,比如只提取industry 为C37 和A15,怎么操作呢?
stkcd year industry
8 2015 "C37"
8 2016 "C37"
8 2017 "C37"
8 2018 "C37"
8 2019 "C37"
12 2015 "C30"
12 2017 "C30"
12 2018 "C30"
12 2019 "C30"
12 2020 "C30"
16 2017 "C39"
16 2018 "C39"
16 2019 "C39"
19 2016 "A15"