r - Create combinations of a binary vector

Question

I would like to create all possible combinations of a binary vector made of a fixed number of 0 and 1. For example: dim(v)=5x1; n1=3; n0=2; In this case I'd like to have something like:

  1,1,1,0,0
  1,1,0,1,0
  1,1,0,0,1
  1,0,1,1,0
  1,0,1,0,1
  1,0,0,1,1
  0,1,1,1,0
  0,1,1,0,1
  0,1,0,1,1
  0,0,1,1,1

I found some help reading this post Create all possible combiations of 0,1, or 2 "1"s of a binary vector of length n but i would like to generate only the combinations I need avoiding any waste of space (I think that the problem will increase explonentially with n)

Answer 1

A slightly faster version of Marat's answer:

f.roland <- function(n, m) {
  ind <- combn(seq_len(n), m)
  ind <- t(ind) + (seq_len(ncol(ind)) - 1) * n
  res <- rep(0, nrow(ind) * n)
  res[ind] <- 1
  matrix(res, ncol = n, nrow = nrow(ind), byrow = TRUE)
}

all.equal(f.2(16, 8), f.roland(16, 8))
#[1] TRUE
library(rbenchmark)
benchmark(f(16,8),f.2(16,8),f.roland(16,8))

#             test replications elapsed relative user.self sys.self user.child sys.child
#2      f.2(16, 8)          100   5.693    1.931     5.670    0.020          0         0
#3 f.roland(16, 8)          100   2.948    1.000     2.929    0.017          0         0
#1        f(16, 8)          100   8.287    2.811     8.214    0.066          0         0