Dear R users? I want to know how to use strata in survival analysis, I want to combine multiple dataset: Coxph(Surv(merged.time.v, merged.event.v)~merged.score+ strata(dataset.v)) So merged.time.v and merged.event.v are from multiple datasets. How should I define dataset.v here? Many thanks yan ********************************************************************** This email and any files transmitted with it are confide...{{dropped:10}}