Match strings against regular expression

The functions give you a concise way to search for regular expressions in character vectors. They are "infix" functions, meaning you write the function between its two arguments: myvector %~% regex.

Usage

x %~l% regex

x %~i% regex

x %~n% regex

x %~m% regex

x %~% regex

... %!~% NA

... %!~l% NA

x %!~i% pattern

Arguments

x

A character vector to search in.

Must be character.

regex

One or more regular expressions.

Must be character.

If more than one regex is supplied, matches to any of the regexes are returned. (See "Multiple regexes" section.)

Details

Each version of the function returns a different type of information about regex matches (if any) in the input vector:

• %~l%: returns logical (TRUE/FALSE) indicating where in x there are matches.

• %~i%: returns integer indicating the indices of matches in x.

• %~n%: returns integer indicating the number (count) of matches in each string.

• %~m%: returns character string of the matched string itself. Returns NA where there is no match.

The basic function (%~%) is the same as %~l%. There is also a negative versions of the l and i functions: giving all strings that don't match the given regular expression. These are %!~%, %!~l%, and %!~i%.

These functions are simply syntactic sugar for existing R regular expression matching functions:

• %~l%: base::grepl()

• %~i%: base::grep()

• %~n%: stringi::stri_count_regex()

• %~m%: stringi::stri_extract_first_regex()

Multiple regexes

If more than one regex is supplied, %~l% and %~i% return the indices where any of the regexes match. In the case of %~n%, each matching regex is counted separately, and they are all summed. In the case of %~m%, all matches (if any) are pasted together, including multiple matches of the same string.