. xtabond2 y L.y x1 x2 x3 x4 x5 x6 x7,gmm(L.y) robust twostep
Favoring speed over space. To switch, type or click on mata: mata set ma
> tafavor space, perm.
unknown egen function max()
                 stata():  3598  Stata returned error
         xtabond2_mata():     -  function returned error
                 <istmt>:     -  function returned error
r(3598);
这又是什么情况呢