Hi R-helpers,
I was trying to put gender='Male' in newdata to create a expected survival
curve for a pseudo cohort by using survfit based on Cox regression. My codes
are shown below:
fit<- coxph(Surv(end, status2)~gender, data=wlwsn1)
Summary(fit)
coef exp(coef) se(coef) z p
genderMale 0.204 1.23 0.0912 2.23 0.025
temp<-data.frame(gender='Male)
wlwsn1curve<-survfit(fit, newdata=temp)
Then I got error message:
Error in `contrasts<-`(`*tmp*`, value = "contr.treatment") :
contrasts can be applied only to factors with 2 or more levels
I do not know what this error message indicates, do I have to recode gender to
0,1 to get it through?
Many thanks
Zhixin
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