Generate random numbers with fixed mean and sd

Question

When generating random numbers in R using rnorm (or runif etc.), they seldom have the exact mean and SD as the distribution they are sampled from.

Answer 1

Since you asked for a one-liner:

rnorm2 <- function(n,mean,sd) { mean+sd*scale(rnorm(n)) }
r <- rnorm2(100,4,1)
mean(r)  ## 4
sd(r)    ## 1