第一步发现:
scatter mpg weight by (tru)
variable by not found
r(111);
第二步:采用常用方法安装
ssc describe by
ssc describe: "by" not found at SSC, type search by
(To find all packages at SSC that start with b, type ssc describe b)
r(601);
####出现错误提示,输入ssc describe b 发现安装包里面的确没有by,和错误601
请大神指点迷津