--begin included message -- I thought this would be trivial, but I can't find a package or function that does this.
I'm hoping someone can guide me to one. Imagine a simple case with two survival curves (e.g. treatment & control). I just want to calculate the difference in KM estimates at a specific time point (e.g. 1 year) plus the estimate's 95% CI. The former is straightforward, but the estimates not so much. -------------- end inclusion ---------- As others have pointed out, use "survfit". Because the curves are step functions, they likely won't have a stored value in the data at exactly 365 days. The summary() function for survival curves allows you to read off the curve's values at any arbitrary time point. A note on standard errors: S(t) +- std is a terrible confidence interval. You will be much more accurate if you use log scale. (Some argue for logit or log-log, in truth they work well.) If n is large enough, however, you should be ok. Terry T. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
