Hi all, I am trying to run regressions with a building by month panel. Each building have a unique building id. There are two types of buildings in the data. First of all, I'd like to run two regressions for each type. After the regression, I would like to compare the coefficients for the two regressions. Here are my code:

Code:
qui reg y x1 x2 i.building_id if building_type==1
eststo m1

qui reg y x1 x2 i.building_id if building_type==2
eststo m2

suest m1 m2, vce(cluster building_id)

test [m1]x1-[m2]x1==0
then I got the following error for the suest fuction:
Code:
building_id: factor variable base category conflict

I understand that this error is reminding me to unify the base of the fixed effect and explicitly specify the base level.

However, the building_id uniquely identify each building, so this variable do not overlap for the Type 1 buildings and the Type 2 buildings. I suppose it is not possible to unify the base level for building_id in the two regressions.

I wonder if there is any alternative ways to compare the coefficients for x1 in the two regressions. Thank you.