Is there a best way to append a list values to a sublist of a list in R?

Question

Say I have a list l containing sublists, and I would like to add an element of a list at the end of each sublist of that list.

> l <- list(c(1,2,3), c(2,1,4), c(4,7,6))
> l
[[1]]
[1] 1 2 3

[[2]]
[1] 2 1 4

[[3]]
[1] 4 7 6

> a <- list(3,5,7)
> a
[[1]]
[1] 3

[[2]]
[1] 5

[[3]]
[1] 7

What I would like is:

> l
[[1]]
[1] 1 2 3 3

[[2]]
[1] 2 1 4 5

[[3]]
[1] 4 7 6 7

I've tried several options, this one gets close, but it still doesn't compute the way I want to, as it adds the whole list at the end of the list.

l <- lapply(l, c, a)

With `lapply()`: `lapply(seq_along(l), \(i) c(l[[i]], a[[i]]))` — s_baldur, May 25 '22 at 09:06

score 6 · Accepted Answer · edited May 25 '22 at 09:32

6

Yes

mapply("c",l,a,SIMPLIFY=FALSE)
[[1]]
[1] 1 2 3 3

[[2]]
[1] 2 1 4 5

[[3]]
[1] 4 7 6 7

edited May 25 '22 at 09:32

Sotos

51,121
6
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66

answered May 25 '22 at 09:00

user2974951

9,535
1
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2

Also `Map("c", l, a)` – s_baldur May 25 '22 at 09:05
1

Or `Map(c, l, a)`. – s_baldur May 25 '22 at 09:34

score 2 · Answer 2 · answered May 25 '22 at 09:08

2

A purrr way:

l <- list(c(1,2,3), c(2,1,4), c(4,7,6))
a <- list(3,5,7)

purrr::map2(l,a, append)

Output:

[[1]]
[1] 1 2 3 3

[[2]]
[1] 2 1 4 5

[[3]]
[1] 4 7 6 7

answered May 25 '22 at 09:08

Julian

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Is there a best way to append a list values to a sublist of a list in R?

2 Answers2

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