I have attempted to follow posting guidelines but I have failed to find out 
what I am doing wrong here.
 I am trying to use lines.survfit to plot a second curve onto a survival 
curve produced by plot.survfit. In my case this is to be a progression free 
survival curve superimposed upon an overall survival curve, but I will 
illustrate my problem using the example given in the help for lines.survfit.
 I would like to have tick marks for censored data points on both curves, so 
I would like to do something like:
 > fit <- survfit(Surv(time, status) ~ sex, pbc,subset=1:312)
> plot(fit[2], mark.time=TRUE, xscale=365.24,
+ xlab='Years', ylab='Survival')
> lines(fit[1], lwd=2, xscale=365.24, mark.time=TRUE)
 but when I do this, no tick marks appear on the second curve. Can anyone 
see what I am doing wrong here?
 Rachel

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