escaping pipe ("|") in a regex
r, regex
Solution
One way to solve this is to use the `\Q...\E` notation to remove the special meaning of any of the characters in `...`. As it says in `?regex`:
If you want to remove the special meaning from a sequence of characters, you can do so by putting them between ‘\Q’ and ‘\E’. This is different from Perl in that ‘$’ and ‘@’ are handled as literals in ‘\Q...\E’ sequences in PCRE, whereas in Perl, ‘$’ and ‘@’ cause variable interpolation.
For example:
> strsplit(x, "[[:space:]]|(?=[\\Q.!?*-|\\E])", perl=TRUE)
[[1]]
[1] "I" "like" "the" "dog" "|" "."
Problem
I have a need to split on words and end marks (punctuation of certain types). Oddly pipe ("|") can count as an end mark. I have code that words on end marks until I try to add the pipe. Adding the pipe makes the `strsplit` every character. Escaping it causes and error. How can I include the pipe int he regular expression? ``` x <- "I like the dog|." strsplit(x, "[[:space:]]|(?=[.!?*-])", perl=TRUE) #[[1]] #[1] "I" "like" "the" "dog|" "." strsplit(x, "[[:space:]]|(?=[.!?*-\|])", perl=TRUE) #Error: '\|' is an unrecognized escape in character string starting "[[:space:]]|(?=[.!?*-\|" ``` The outcome I'd like: ``` #[[1]] #[1] "I" "like" "the" "dog" "|" "." #pipe is an element ```