CODEWITHSUNDEEP
rsplit
Etienne Low-Décarie
Etienne Low-Décarie

Reputation: 13443

R strsplit with multiple unordered split arguments?

Given a character string

test_1<-"abc def,ghi klm"
test_2<-"abc, def ghi klm"

I wish to obtain

"abc"
"def"
"ghi"

However, using strsplit, one must know the order of the splitting values in the string, as strsplit uses the first value to do the first split, the second to do the second... and then recycles.

But this does not:

strsplit(test_1, c(",", " "))
strsplit(test_2, c(" ", ","))

strsplit(test_2, split=c("[:punct:]","[:space:]"))[[1]]

I am looking to split the string wherever I find any of my splitting values in a single step.

Upvotes: 66

Views: 59741

Answers (4)

IRTFM
IRTFM

Reputation: 263331

Actually strsplit uses grep patterns as well. (A comma is a regex metacharacter whereas a space is not; hence the need for double escaping the commas in the pattern argument. So the use of "\\s" would be more to improve readability than of necessity):

> strsplit(test_1, "\\, |\\,| ")  # three possibilities OR'ed
[[1]]
[1] "abc" "def" "ghi" "klm"

> strsplit(test_2, "\\, |\\,| ")
[[1]]
[1] "abc" "def" "ghi" "klm"

Without using both \\, and \\, (note extra space that SO does not show) you would have gotten some character(0) values. Might have been clearer if I had written:

> strsplit(test_2, "\\,\\s|\\,|\\s")
[[1]]
[1] "abc" "def" "ghi" "klm"

@Fojtasek is so right: Using character classes often simplifies the task because it creates an implicit logical OR:

> strsplit(test_2, "[, ]+")
[[1]]
[1] "abc" "def" "ghi" "klm"

> strsplit(test_1, "[, ]+")
[[1]]
[1] "abc" "def" "ghi" "klm"

Upvotes: 78

zhan2383
zhan2383

Reputation: 679

 test_1<-"abc def,ghi klm"
 test_2<-"abc, def ghi klm"
 key_words <- c("abc","def","ghi")
 matches <- str_c(key_words, collapse ="|")
 str_extract_all(test_1, matches)
 str_extract_all(test_2, matches)

Upvotes: 1

jthetzel
jthetzel

Reputation: 3623

In case you don't like regular expressions, you can call strsplit() multiple times:

strsplits <- function(x, splits, ...)
{
    for (split in splits)
    {
        x <- unlist(strsplit(x, split, ...))
    }
    return(x[!x == ""]) # Remove empty values
}

strsplits(test_1, c(" ", ","))
# "abc" "def" "ghi" "klm"
strsplits(test_2, c(" ", ","))
# "abc" "def" "ghi" "klm"

Updated for the added example

strsplits(test_1, c("[[:punct:]]","[[:space:]]"))
# "abc" "def" "ghi" "klm"
strsplits(test_2, c("[[:punct:]]","[[:space:]]"))
# "abc" "def" "ghi" "klm"

But if you are going to use regular expressions, you might as well go with @DWin's approach:

strsplit(test_1, "[[:punct:][:space:]]+")[[1]]
# "abc" "def" "ghi" "klm"
strsplit(test_2, "[[:punct:][:space:]]+")[[1]]
# "abc" "def" "ghi" "klm"

Upvotes: 9

danas.zuokas
danas.zuokas

Reputation: 4643

You could go with strsplit(test_1, "\\W").

Upvotes: 6

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