R Under development (unstable) (2024-12-12 r87438 ucrt) -- "Unsuffered Consequences"
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> library(survival)
> #
> # Check out intercept/interaction for Frank H
> #
> age2 <- lung$age - 50
> fit1 <- coxph(Surv(time, status) ~ age * strata(sex), lung)
> fit2 <- coxph(Surv(time, status) ~ age2*strata(sex), lung)
> 
> tdata <- data.frame(age=50:60, age2=0:10, sex=c(1,2,1,2,1,2,1,2,1,2,1))
> 
> surv1 <- survfit(fit1, tdata)
> surv2 <- survfit(fit2, tdata)
> # The call won't match, nor the newdata data frame
> icall <- match(c("newdata", "call"), names(surv1))
> all.equal(unclass(surv1)[-icall], unclass(surv2)[-icall])
[1] TRUE
> 
> 
> # It should match what I get with a single strata fit
> 
> fit3 <- coxph(Surv(time, status) ~ age, data=lung,
+               init=fit1$coef[1], subset=(sex==1), iter=0)
> surv1b <- survfit(fit3, newdata=list(age=c(50,52, 54)))
> all.equal(c(surv1b$surv), surv1[c(1,3,5)]$surv)
[1] TRUE
> 
> 
> 
> 
> proc.time()
   user  system elapsed 
   0.76    0.14    0.89