survival package - calculating probability to survive a given time

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i try to calculate the probabilty to survive a given time by using the 
estimated survival curve by kaplan meier.

What is the right way to do that? as far as is see i cannot use the 
predict-methods from the survival package?
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The survfit function directly estimates the probability you want, no
predict method is needed.  It is similar to quantile(x, 1:9/10), in that
you would not use predict on that either.

As to getting the value at a specific time, use
	summary(fit, time=20)
This correctly interpolates the step function when "20" is exactly one
of the event times.

Terry Therneau