foreach x of varlist $yandxforhausman{
  2. by state:egen mean `x`=mean(`x`)
  3. gen md`x`=`x`-mean`x`
  4. gen red `x`=`x`-theta*mean`x`
  5. }
{ required
r(100);

我的{也确实是英文符号鸭，不知道为什么一直报错，感谢各位老师帮助！