[R] reorder a list

[William Dunlap]

f <- function (x) {
    lengths <- vapply(x, FUN = length, FUN.VALUE = 0L)
    split(rep(seq_along(x), lengths), unlist(x, use.names = FALSE))
}
f(A1) # gives about what you want (has, e.g., name 23, not position
23, in output)
Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Tue, Jul 8, 2014 at 9:39 AM, Lorenzo Alfieri <alfios17 at hotmail.com> wrote:
> Hi,
> I'm trying to find a way to reorder the elements of a list.
> Let's say I have a list like this:
> A1<-list(c(1:4),c(2,4,5),23,c(4,5,13))
>
>> A1
> [[1]]
> [1] 1 2 3 4
>
> [[2]]
> [1] 2 4 5
>
> [[3]]
> [1] 23
>
> [[4]]
> [1]  4  5 13
>
> All the elements included in it are values, while each sublist is a time index
> Now, I'd like to reorder the list (without looping) so to obtain one sublist for each value, which include all the time indices where each value appears.
> In other words, the result should look like this:
>>A2
> [[1]]
> [1] 1
>
> [[2]]
> [1] 1 2    #because value "2" appears in the time index [[1]] and [[2]] of A1
>
> [[3]]
> [1] 1
>
> [[4]]
> [1] 1 2 4
>
> [[5]]
> [1] 2 4
>
> [[13]]
> [1] 4
>
> [[23]]
> [1] 3
>
> Any suggestion?
> Thanks
> Alfio
>
>
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>
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