[R] survival::survfit,plot.survfit

[Jeff Xu]

I am confused when trying the function survfit.
my question is:  what does the survival curve given by plot.survfit mean?
is it the survival curve with different covariates at different points?
or just the baseline survival curve?

for example, I run the following code and get the survival curve

####
library(survival)
fit<-coxph(Surv(futime,fustat)~resid.ds+rx+ecog.ps,data=ovarian)
plot(survfit(fit,type="breslow"))
summary(survfit(fit,type="breslow"))
####

for the first two failure points, we have s(59|x1)=0.971, s(115|x2)=0.942
how can we guarantee that s(59|x1) is always greater than s(115|x2)?
since s(59|x1)=s_0(59)^exp(\beta'x1) and s(115|x2)=s_0(115)^exp(\beta'x2),
we can manipulate covariates to make s(59|x1) < s(115|x2), right?
do I miss anything?

thanks in advance
Jeff 

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