给定一个向量，返回最大为n的所有组合的列表 [英] Given a vector, return a list of all combinations up to size n

问题描述

我正在尝试在R中编写一个函数，给定一个向量和最大大小n，它将返回该向量中所有元素的组合，直到大小n。

I'm trying to write a function in R that, given a vector and a maximum size n, will return all the combinations of elements from that vector, up to size n.

例如：

multi_combn(LETTERS[1:3], 2)

会产生的收益：

[[1]]
[1] "A"

[[2]]
[1] "B"

[[3]]
[1] "C"

[[4]]
[1] "A" "B"

[[5]]
[1] "A" "C"

[[6]]
[1] "B" "C"

我想出了一种巧妙的方法来运行 combn ，每个大小最多为n，但是我可以似乎没有将结果合并到一个列表中。有建议吗？

I've figured out an inelegant way to run combn for each size up to n, but I can't seem to combine the results into a single list. Any suggestions?

推荐答案

尝试一下：

multi_combn <- function(dat, n) {
    unlist(lapply(1:n, function(x) combn(dat, x, simplify=F)), recursive=F)
}

返回

> multi_combn(LETTERS[1:3], 2)
[[1]]
[1] "A"

[[2]]
[1] "B"

[[3]]
[1] "C"

[[4]]
[1] "A" "B"

[[5]]
[1] "A" "C"

[[6]]
[1] "B" "C"

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