How to generate a matrix of combinations

r cross-join

expand.grid(c(-1,1), c(-1,1), c(-1,1), c(-1,1), c(-1,1))

r cross-join

To generalize Greg's answer:

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

r cross-join

Alternative from data.table package is slightly faster compared to expand.grid:

library(data.table)  CJ(c(-1,1), c(-1,1), c(-1,1), c(-1,1), c(-1,1))

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