How to fill matrix with random numbers in R?

Question

expand.grid(i=rexp(5,rate=0.1)) 

It creates just one col but is there some way to multiply this easily to 5 cols? I mean the matlab-way-of-doing-things like rand('exp', 0.1, 10,20) (creating a matrix with exponentially-distributed-random-numbers with mean 0.1 of size 10x20), how?

Answer 1

Use the matrix function:

matrix(rexp(200, rate=.1), ncol=20) 

ETA: If you want to do it without repeating the 200, you can define a function to do so:

fill.matrix = function(expr, nrow=1, ncol=1) {     matrix(eval(expr, envir=list(x=nrow*ncol)), nrow=nrow, ncol=ncol) }  fill.matrix(rexp(x, rate=.1), nrow=10, ncol=20) 

The x thus becomes the dummy variable you're talking about. Is that what you're looking for?

Answer 2

you can do something like:

matrix(rexp(200), 10) 

And of course use what ever distribution you want.