I am trying the merge hundreds lists to one.Not intend to modify the contents of lists, I just want to sequentially combine the lists. The names of lists has some rules, so I want to use for-loop with get() and paste0() function. But The for-loop only showed me NULL value. Here is the simple example which reflect my case.
These are the lists what I want to merge.
list_a <- list(1, 2, 3, 4)
list_b <- list('a', 'b', 'c', 'd')
When I use list function directly, I can sucessfully get what I wanted
> list(list_a, list_b)
[[1]]
[[1]][[1]]
[1] 1
[[1]][[2]]
[1] 2
[[1]][[3]]
[1] 3
[[1]][[4]]
[1] 4
[[2]]
[[2]][[1]]
[1] "a"
[[2]][[2]]
[1] "b"
[[2]][[3]]
[1] "c"
[[2]][[4]]
[1] "d"
However, when I use for loop, I just could draw NULL value like below
naming <- c("list_a", "list_b")
aa <- list()
result <- for(i in 1:length(naming)){
aa[[i]] <- get(naming[i])
}
> result
NULL
However, mysteriously, when I just dissolved the for-loop, I could get the right answer.
> list(get(naming[1]), get(naming[2]))
[[1]]
[[1]][[1]]
[1] 1
[[1]][[2]]
[1] 2
[[1]][[3]]
[1] 3
[[1]][[4]]
[1] 4
[[2]]
[[2]][[1]]
[1] "a"
[[2]][[2]]
[1] "b"
[[2]][[3]]
[1] "c"
[[2]][[4]]
[1] "d"
I don't know the reason why my for-loop not working. I attempted the designate the global enviorment in the function but it was not working too, only show NULL result.
Please give me some ideas to fix it.
I think that the problem is in your syntax, since you are setting the result variable equal to a loop. This code works for me:
result <- list()
for(i in 1:length(naming)) {
result[[i]] <- get(naming[i])
}
result
[[1]]
[[1]][[1]]
[1] 1
[[1]][[2]]
[1] 2
[[1]][[3]]
[1] 3
[[1]][[4]]
[1] 4
[[2]]
[[2]][[1]]
[1] "a"
[[2]][[2]]
[1] "b"
[[2]][[3]]
[1] "c"
[[2]][[4]]
[1] "d"