创建二进制矢量的组合 [英] Create combinations of a binary vector

问题描述

我想创建由固定数量的0和1。例如二元载体的所有可能的组合：
暗淡（V）= 5X1; N1 = 3; N0 = 2;
在这种情况下，我想有这样的：

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

我发现了一些帮助阅读这篇文章
<一href=\"http://stackoverflow.com/questions/27826508/create-all-possible-combiations-of-0-1-or-2-1s-of-a-binary-vector-of-length-n\">Create的0,1，或2英寸的所有可能combiations 1 QUOT氏长度为n 的二元载体的
但我想生成只需要我避免空间浪费任何组合（我认为这个问题将有n explonentially增加）

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)

推荐答案

萨芬的回答稍微更快的版本：

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

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