[R] Weighted Kaplan-Meier estimates with R (with confidence intervals)?

[rm]

As part of a research paper, I would like to draw both weighted and
unweighted Kaplan-Meier estimates, the weight being the ’importance’ of the
each project to the mass of projects whose survival I’m trying to estimate.

I know that the function survfit in the package survival accepts weights and
produces confidence intervals. However, I suspect that the confidence
intervals may not be correct. The reason why I suspect this is that
depending on how I define the weights, I get very different confidence
intervals, e.g.

require(survival) 
s <- Surv(c(50,100),c(1,1)) 
sf <- survfit(s~1,weights=c(1,2)) 
plot(sf) 

vs.

require(survival) 
s <- Surv(c(50,100),c(1,1)) 
sf <- survfit(s~1,weights=c(100,200)) 
plot(sf)

Any suggestions would be more than welcome!




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