Convert a list of lists to a character vector

r string list character sapply
dan picture dan · Jan 6, 2016 · Viewed 24k times · Source

I have a list of lists of characters. For example:

l <- list(list("A"),list("B"),list("C","D"))

So as you can see some elements are lists of length > 1.

I want to convert this list of lists to a character vector, but I'd like the lists with length > 1 to appear as a single element in the character vector.

the unlist function does not achieve that but rather:

> unlist(l)
[1] "A" "B" "C" "D"

Is there anything faster than:

sapply(l,function(x) paste(unlist(x),collapse=""))

To get my desired result:

"A"  "B"  "CD"

Answer

IRTFM picture IRTFM · Jan 6, 2016

You can skip the unlist step. You already figured out that paste0 needs collapse = TRUE to "bind" sequential elements of a vector together:

> sapply( l, paste0, collapse="")
[1] "A"  "B"  "CD"

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