如何遍历 R 中长度为 n 的列表的长度为 k 的子集？

Question

I am given two numbers n and k with 0 < k < n . How can I loop over all possible combinations of subsets of length k?

Eg I have x <- 1:10 . Then I want to do

for (y in c(c(1,2,3), c(1,2,4), c(1,2,5), ..., c(8, 9, 10))){
   ...
}

Answer 1

You can use combn to get an array of all the subsets, then convert that into a list using asplit . Just iterate along this list.

For example, the following code will print out all the length-3 subsets of x:

x <- 1:10
n <- 10
k <- 3

subsets <- asplit(combn(n, k), 2)

for(i in subsets) {
  print(x[i])
}