foreach x of varlist $yandxforhausman{
  2. by company:egen mean'x'=mean('x')
  3. gen md'x'='x'-mean'x'
  4. gen red'x'='x'-theta*mean'x'
  5. }  
系统提示5.后面的大括号为invalid command name.该怎么解决呢。不懂什么原因啊，在线等，谢谢啦。