My goal is to divide a list into n groups in all possible combinations (where the group has a variable length).
I found the same question answered here (Python environment), but I'm unable to replicate it in the R environment.
Could anyone kindly help me? Thanks a lot.
If you want an easy implementation for the similar objective, you can try listParts from package partitions, e.g.,
> x <- 4
> partitions::listParts(x)
[[1]]
[1] (1,2,3,4)
[[2]]
[1] (1,2,4)(3)
[[3]]
[1] (1,2,3)(4)
[[4]]
[1] (1,3,4)(2)
[[5]]
[1] (2,3,4)(1)
[[6]]
[1] (1,4)(2,3)
[[7]]
[1] (1,2)(3,4)
[[8]]
[1] (1,3)(2,4)
[[9]]
[1] (1,4)(2)(3)
[[10]]
[1] (1,2)(3)(4)
[[11]]
[1] (1,3)(2)(4)
[[12]]
[1] (2,4)(1)(3)
[[13]]
[1] (2,3)(1)(4)
[[14]]
[1] (3,4)(1)(2)
[[15]]
[1] (1)(2)(3)(4)
where x is the number of elements in the set, and all partitions denotes the indices of elements.
If you want to choose the number of partitions, below is a user function that may help
f <- function(x, n) {
res <- listParts(x)
subset(res, lengths(res) == n)
}
such that
> f(x, 2)
[[1]]
[1] (1,2,4)(3)
[[2]]
[1] (1,2,3)(4)
[[3]]
[1] (1,3,4)(2)
[[4]]
[1] (2,3,4)(1)
[[5]]
[1] (1,4)(2,3)
[[6]]
[1] (1,2)(3,4)
[[7]]
[1] (1,3)(2,4)
> f(x, 3)
[[1]]
[1] (1,4)(2)(3)
[[2]]
[1] (1,2)(3)(4)
[[3]]
[1] (1,3)(2)(4)
[[4]]
[1] (2,4)(1)(3)
[[5]]x
[1] (2,3)(1)(4)
[[6]]
[1] (3,4)(1)(2)
Update
Given x <- LETTERS[1:4], we can run
res <- rapply(listParts(length(x)), function(v) x[v], how = "replace")
such that
> res
[[1]]
[1] (A,B,C,D)
[[2]]
[1] (A,B,D)(C)
[[3]]
[1] (A,B,C)(D)
[[4]]
[1] (A,C,D)(B)
[[5]]
[1] (B,C,D)(A)
[[6]]
[1] (A,D)(B,C)
[[7]]
[1] (A,B)(C,D)
[[8]]
[1] (A,C)(B,D)
[[9]]
[1] (A,D)(B)(C)
[[10]]
[1] (A,B)(C)(D)
[[11]]
[1] (A,C)(B)(D)
[[12]]
[1] (B,D)(A)(C)
[[13]]
[1] (B,C)(A)(D)
[[14]]
[1] (C,D)(A)(B)
[[15]]
[1] (A)(B)(C)(D)
