Dear List, After including cluster() option the coxreg (from eha package) produces results slightly different than that of coxph (from survival) in the following time-dependent treatment effect calculation (example is used just to make the point). Will appreciate any explaination / comment.
cheers, Ehsan ############################ require(survival) require(eha) data(heart) # create weights follow <- heart$stop - heart$start fit <- glm(transplant ~ age + surgery + year + follow, data=heart, family = binomial) heart$iptw <- ifelse(heart$transplant == 0, 1 - predict(fit, type = "response"), predict(fit, type = "response")) summary(heart$iptw) # no weights (basic calculation) fit0 <- coxph(Surv(start,stop,event)~transplant, data=heart) fit0 # fit with coxph without case-weights fit1 <- coxreg(Surv(start,stop,event)~transplant, data=heart) fit1 # fit with coxreg from eha without case-weights # coxph fit2 <- coxph(Surv(start,stop,event)~transplant + cluster(id), data=heart, weights = iptw, robust = T) fit2 # fit with coxph having robust and cluster option fit3 <- coxph(Surv(start,stop,event)~transplant + cluster(id), data=heart, weights = iptw) fit3 # fit with coxph having cluster option fit4 <- coxph(Surv(start,stop,event)~transplant, data=heart, weights = iptw) fit4 # fit with coxph # coxreg fit5 <- coxreg(Surv(start,stop,event)~transplant + cluster(id), data=heart, weights = iptw) fit5 # fit with coxreg from eha having cluster option fit6 <- coxreg(Surv(start,stop,event)~transplant, data=heart, weights = iptw) fit6 # fit with coxreg from eha ############################ > exp(coef(fit3)) # HR from coxph having cluster option transplant1 0.3782417 > exp(coef(fit4)) # HR from coxph transplant1 0.3782417 > exp(coef(fit5))[1] # HR from coxreg having cluster option transplant1 0.3645507 > exp(coef(fit6))[1] # HR from coxreg transplant1 0.3782417 ############################ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
