probit可以正常跑出数据，但是tobit模型如果我加入i.province中就报错了。
报错如下。
. asdoc tobit lhealth_ins_cost oldsum $cc i.province , ll(0)  save(C:\Users\花\Desktop\数据处理\回归\稳健性-
> tobit.doc)  nest replace
no; data are mi set
    Use mi fvset to set or query these data; mi fvset has the same syntax as fvset.

    Perhaps you did not type fvset.  Some commands call fvset to obtain information about the settings.
    In that case, that command is not appropriate for running directly on mi data.  Use mi extract to
    select the data on which you want to run the command, which is probably m=0.
r(119);

我搜了好久还是没有头绪，发帖求助，如果求助格式有误还请见谅。救急，谢谢！