老师您好。请问：PH假定不成立，加上时间和暴露的交互项应该如何操作呢？我的stata提示不收敛，而且exactp 好几分钟了还算不出来，不懂求指教~~

我的程序： stcox x#c.time  x age gender i.(edugp spouse drinkgp smkgp fruit healthgp) ib2.bmi_gp 

提示：

flat region resulting in a missing likelihood

 convergence not achieved         You have estimated a maximum likelihood model, and Stata's         maximization procedure failed to converge to a solution;         see help maximize.  Check if the model is identified.