How to obtain all combinations of the columns of a data frame taken by 2?

combinations, dataframe, r

Solution

combn(X.df, 2, simplify=FALSE)
[[1]]
  V1 V2
1  2  4
2  5  7
3  3  5
4  4  5
5  3  6
6  4  5

[[2]]
  V1 V3
1  2  3
2  5  1
3  3  8
4  4  1
5  3  1
6  4  6

[[3]]
  V1 V4
1  2  1
2  5  2
3  3  2
4  4  1
5  3  3
6  4  1

[[4]]
  V2 V3
1  4  3
2  7  1
3  5  8
4  5  1
5  6  1
6  5  6

[[5]]
  V2 V4
1  4  1
2  7  2
3  5  2
4  5  1
5  6  3
6  5  1

[[6]]
  V3 V4
1  3  1
2  1  2
3  8  2
4  1  1
5  1  3
6  6  1

Problem

Suppose I have this data frame: ``` matrix(c(2,4,3,1,5,7,1,2,3,5,8,2,4,5,1,1,3,6,1,3,4,5,6,1),nrow=6,ncol=4,byrow = TRUE)->X as.data.frame(X)->X.df V1 V2 V3 V4 1 2 4 3 1 2 5 7 1 2 3 3 5 8 2 4 4 5 1 1 5 3 6 1 3 6 4 5 6 1 ``` then I would like to obtain a list of a set of data frames containing all combinations of columns taken by 2, without repetition, and avoiding any column with itself. That means, a list of dataframes with the following headers: ``` V1,V2 V1,V3 V1,V4 V2,V3 V2,V4 V3,V4 ``` Any idea of how to do this?

Original source