R tip: Extracting median from survfit object
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A colleague wanted to extract the median value from a survival analysis object, which turned out to be a pain as the value is not stored in the object, but calculated on the fly by a print method.Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
> library(survival)But how do you get the median value? Some googling came up with this link. The answer is rather clunky:
> fit <- coxph(Surv(time, status) ~ x, data=aml)
> survfit(fit)
Call: survfit(formula = fit)
records n.max n.start events median 0.95LCL 0.95UCL
23 23 23 18 30 18 45
> x <- read.table(textConnection(capture.output(survfit(fit))),skip=2,header=TRUE)
> x$median
[1] 30
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