R strsplit with multiple unordered split arguments?
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"
You could go with strsplit(test_1, "\\W")
.
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"
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)