How to find a vector length of 'n' values, where each value is a mean of 'm' random elements of data in R?

How 开发者_开发问答to find a vector length of 'n' values, where each value is a mean of 'm' random elements of data in R?

Code below is for sampling with replacement.

random_nm<- function(n,m,v){
      x <- sample(seq(length(v)),n*m,replace=TRUE)
      rowMeans(matrix(v[x],nrow=n,ncol=m))
}

dat <- rnorm(100)
random_nm(5,20,dat)

[1]  0.05149423 -0.16239828  0.45485354 -0.10758954 -0.13597127

If you want samples without replacement first line of function random_rn has to be changed.