Question

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.

Answer 1

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"