Displaying 1 result from an estimated 1 matches for "othercovars".
2009 Jan 07
0
Frailty by strata interactions in coxph (or coxme)?
...al, receiving Z(k,i) treatment (0-1) in the kth center as:
lambda(k,i)=lambda(0,k)*exp(b*Z(k,i)+om(k)*Z(k,i))
where om(k) = center specific effect - mean treatment effect ~ distributed as a (log-) gamma or normal frailty.
I coded this model in R as:
r1<-coxph(Surv(d,e)~treat*frailty(center)+othercovars+strata(center))
coxph produces a table with the coefficients and standard errors for:
a) the treatment variable
b) the covariates as well as
c) the treatment x frailty interaction effect.
but the main effect of frailty is estimated to be zero (which I expected, since it is "absorbed" in...