arlionn 发表于 2014-1-16 20:48 
bysort industry year: egen x_mean = mean(x)
bysort industry year: egen x_med = median(x)
stkcd date year industry company
2234 2015/3/27 2015 A 12.44741
2477 2015/5/29 2015 A 10.40656
300087 2015/7/6 2015 A 10.52499
735 2016/4/18 2016 A 13.20506
2505 2016/5/11 2016 A 10.97084
2069 2016/5/16 2016 A 11.99248
798 2016/5/25 2016 A 10.72388
2679 2016/5/30 2016 A 12.17057
592 2016/6/13 2016 A 13.6935
300087 2016/6/30 2016 A 8.953562
300143 2016/7/5 2016 A 14.64838
请问老师如何计算同年同行业公司日期(date)之前的company行业均值呢