Hi, I am a graduate student.

First, I will explain my situation.
I have a dependent variable(score), regressors(v1,v2,v3), and a variable distinguishing group (named agedummy).
In this situation, I want to run regression for each group(young and old).
So, I run a command as following.

.xtset pid wave
.bysort agedummy: xtreg score v1 v2 v3, fe vce(robust)

But, stata shows me a error massage "the by prefix may not be used with vce() option.

In this case, how can I run the fixed effect regression with robust vce??
Please, help me!