[R] What's the baseline model when using coxph with factor variables?

[Andreas Schlicker]

Hi all,

I'm trying to fit a Cox regression model with two factor variables but 
have some problems with the interpretation of the results. Considering 
the following model, where var1 and var2 can assume value 0 and 1:

coxph(Surv(time, cens) ~ factor(var1) * factor(var2),  data=temp)

What is the baseline model? Is that considering the whole population or 
the case when both var1 and var2 = 0?

Kind regards,
andi