如何在不考虑顺序的情况下生成所有可能的向量组合? [英] How to generate all possible combinations of vectors without caring for order?

问题描述

在数据框中，我有一列包含字符串.假设它看起来像这样:

In a data frame, I have one column containing character strings. Let's say it looks like this:

x <- unique(df[,1])
x
"A" "A" "B" "B" "B" "C"

我想在不关心顺序的情况下将唯一字符串的所有可能组合设为 2 组，所以 A, B 与 B, A 相同code>，我不想得到与 A, A 这样的组合相同的值.到目前为止，我得到了这一点:

I'd like to get all possible combinations of the unique character strings as sets of 2 without caring about their order, so A, B is the same as B, A, and I don't want to get same values as combination like A, A. So far, I got until this point:

comb <- expand.grid(x, x)
comb <- comb[which(comb[,1] != comb[,2]),]

但是这仍然存在以不同顺序排列具有相同字符串组合的行的问题.我该如何摆脱这种情况?

But this still leaves the problem of having rows with the same combination of strings in a different order. How do I get rid of this?

推荐答案

utils 包中有 combn 函数:

t(combn(LETTERS[1:3],2))
#      [,1] [,2]
# [1,] "A"  "B" 
# [2,] "A"  "C" 
# [3,] "B"  "C"

我有点困惑为什么你的 x 有重复的值.

I'm a little confused as to why your x has duplicated values.

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