黃河泉 发表于 2020-8-17 08:51 
或 (ssc install runby) 试试
老师,试了您说的代码,跑出的结果有问题,给的回复是这样的
. runby sk, by(Liscd)
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Number of by-groups = 3,156
by-groups with errors = 3,156
by-groups with no data = 0
Observations processed = 76,606
Observations saved = 0
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这是为什么呢