Interpreting Weibull parameters from survreg

Question

I am trying to generate an inverse Weibull distribution using parameters estimated from survreg in R. By this I mean I would like to, for a given probability (which will be a ra

Answer 1

The key is that the shape parameter the rweibull generates is the inverse of the shape parameter the survreg inputs

Answer 2

This is explained in the manual page, ?survreg (in the "examples" section).

library(survival)
y <- rweibull(1000, shape=2, scale=5)
r <- survreg(Surv(y)~1, dist="weibull")
a <- 1/r$scale      # Approximately 2
b <- exp( coef(r) ) # Approximately 5
y2 <- b * ( -ln( 1-runif(1000) ) ) ^(1/a)
y3 <- rweibull(1000, shape=a, scale=5)
# Check graphically that the distributions are the same
plot(sort(y), sort(y2))
abline(0,1)