Generating random sample from the quantiles of unknown density in R [duplicate]

Answer 1

Rejection sampling is easy enough:

   drawF <- function(n) {  
     f <- function(x) ((x-1)^2) * exp(-(x^3/3-2*x^2/2+x))
     x <- runif(n, 0 ,4)
     z <- runif(n) 
     subset(x, z < f(x)) # Rejection
   }

Not the most efficient but it gets the job done.