CODEWITHSUNDEEP
rstringliststrsplit
Kyle Weise
Kyle Weise

Reputation: 879

Split a list whose elements are multiple element lists

Say I have a list a which is defined as:

a <- list("aaa;bbb", "aaa", "bbb", "aaa;ccc")

I want to split this list by semicolon ;, get only unique values, and return another list. So far I have split the list using str_split():

a <- str_split(a, ";")

which gives me

> a
[[1]]
[1] "aaa" "bbb"

[[2]]
[1] "aaa"

[[3]]
[1] "bbb"

[[4]]
[1] "aaa" "ccc"

How can I manipulate this list (using unique()?) to give me something like 

[[1]]
[1] "aaa" 

[[2]]
[1] "bbb"

[[3]]
[1] "ccc"

or more simply,

[[1]]
[1] "aaa" "bbb" "ccc"

Upvotes: 0

Views: 2383

Answers (2)

lmo
lmo

Reputation: 38510

One alternative in base R is to use rapply which applies a function to each of the inner most elements in a nested list and returns the most simplified object possible by default. Here, it returns a vector of characters.

unique(rapply(a, strsplit, split=";"))
[1] "aaa" "bbb" "ccc"

To return a list, wrap the output in list

list(unique(rapply(a, strsplit, split=";")))
[[1]]
[1] "aaa" "bbb" "ccc"

Upvotes: 3

Miha
Miha

Reputation: 2874

One option is to use list() with unique() and unlist() inside your list.

    # So first you use your code
    a <- list("aaa;bbb", "aaa", "bbb", "aaa;ccc")
    # Load required library 
    library(stringr) # load str_split
    a <- str_split(a, ";")
    # Finally use list() with unique() and unlist()
    list(unique(unlist(a)))
    # And the otuput
    [[1]]
    [1] "aaa" "bbb" "ccc"

Upvotes: 3

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