How do I calculate the probability for a given quantile in R?

Question

Using R, it is trivial to calculate the quantiles for given probabilities in a sampled distribution:

x <- rnorm(1000, mean=4, sd=2)
quantile(x, .9) # resu         


        

Answer 1

Just for convenience, this function helps:

quantInv <- function(distr, value) ecdf(distr)(value)
set.seed(1)
x <- rnorm(1000, mean=4, sd=2)
quantInv(x, c(4, 5, 6.705755))
[1] 0.518 0.685 0.904