Flatten nested lists in a list

Question

I have a list with nested lists inside.

LIST2 <- list(list("USA","WY","TX","AZ","Canada", "CA", "NY", 'Russia', 'NY'), 
             list(c("USA","Canada","CA","WY", 'China', 'AZ', 'AZ', 'AZ', 'WY')), 
             list(c("USA","Australia","CA","AR", 'AZ', 'WY', 'New Zealand', 'Japan', 'Japan', 'NJ')),
             list(list('Australia', 'Australia', 'Japan', 'Malaysia' )),
             list(c('USA', 'Australia', 'Japan', 'Malaysia' )))

I would like to flatten somehow the 1st and 4th list so they are same form as the rest of them. Is this possible?

Maybe `lapply(LIST2, function(i) list(unlist(i, recursive = TRUE))) ` ? — zx8754, Jan 25 '18 at 12:45

score 17 · Answer 1 · answered Jan 25 '18 at 12:48

17

We could use rapply

lapply(LIST2, rapply, f = c)

answered Jan 25 '18 at 12:48

akrun

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Nice one, keep forgetting about rapply. I think OP wants output as list of lists. – zx8754 Jan 25 '18 at 12:49
2

@zx8754 Thanks, then wrapping with `list` as you have done would be the way to go `lapply(LIST2, function(x) list(rapply(x, f = c)))` – akrun Jan 25 '18 at 12:54
1

nice - also preserved the structure of my data better than [this solution](https://stackoverflow.com/questions/42739419/r-convert-nested-list-into-a-one-level-list) Not sure though why my output list is still nested one level deep. But this is a small problem in comparison to my previous highly nested list with elements of unequal length – Simone Nov 03 '21 at 08:15

score 9 · Accepted Answer · answered Jan 25 '18 at 12:47

9

Loop through the list, unlist recursively, then return as a list:

lapply(LIST2, function(i) list(unlist(i, recursive = TRUE)))

answered Jan 25 '18 at 12:47

zx8754

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score 4 · Answer 3 · answered Jan 25 '18 at 12:47

4

this should do it for you:

LIST2 <- lapply(LIST2, unlist)

answered Jan 25 '18 at 12:47

waskuf

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Flatten nested lists in a list

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