How to generate a matrix of combinations

Question

I have 5 items each of which can take on the value of 1 or -1. I want to generate a matrix that consists of rows of the possible combinations. The order of the items does no

Answer 1

To generalize Greg's answer:

N   <- 5
vec <- c(-1, 1)
lst <- lapply(numeric(N), function(x) vec)
as.matrix(expand.grid(lst))