[R] obtaining the values for the hazard function in a cox regression

Bob Green bgreen at dyson.brisnet.org.au
Sat Mar 14 09:14:41 CET 2009

Hello ,

I am hoping for some advice regarding obtaining the values for the 
hazard function in a cox regression that I have undertaken. I have a 
model in the following form, analysed with the package survival (v. 
2.34-1) and a log-log plot obtained using Design (v. 2.1-2).

For two variables, the lines in the survival curves crossed. The 
statistician I been obtaining advice from (who does not use R) asked 
me to obtain the hazard function values. I am wanting to confirm 
whether basehaz is the correct command to obtain such values, to 
better understand what is occurring in the log plots.

Below is the code that I have been using.  Any assistance is appreciated,



recidivismv <- read.csv("g://Chapsurv_v.csv",header=T)
cox.V <- coxph(Surv(intDaysUntilFVPO, Event_v) ~ intAgeAtMHCIndex + 
PRE + group + MHC + strGender, data = recidivismv)
summary (cox.V)

# produces a log-log plot

mvfit <- survfit (Surv(recidivismv$intDaysUntilFVPO, 
recidivismv$Event_v) ~ MHC, data = recidivismv)
neg.ll <- function(mvfit) -log(-log(mvfit))
library (Design)
survplot(mvfit, fun = neg.ll, conf = "none", logt=TRUE)

# hazard values
mhc2 <- coxph (Surv(recidivismv$intDaysUntilFVPO, 
recidivismv$Event_v) ~ MHC, data = recidivismv)

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