[R] Using contrast with cox models

Patterson, Stuart spatterson at RVC.AC.UK
Mon Nov 21 15:47:48 CET 2016


I was wondering if I could get some advice on the following question please:

I have a time-dependent cox model with three variables, each of which interacts with the other two. So my final model is:

fit12<-coxph(formula = Surv(data$TimeIn, data$Timeout, data$Status) ~ data$Year+data$Life_Stg+data$prev.tb +data$prev.tbdata$Life_Stg + data$Yeardata$Life_Stg + data$Year*data$prev.tb + frailty(data$Natal_Group), data = data)

For my variables, there are 3 categories of year, three of year, and prev.tb is a binary variable. Because of the interactions, when I present the results, I want to present the Hazard ratio, 95% CI, and p value for each combination of the three variables. How do I get R to give me these values please?

I think that the contrast function does this for other models but does not work for coxph?

Many thanks

Stuart Patterson

Royal Veterinary College, University of London

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