Match Regular Expressions with a Nicer 'API'

Description

A small wrapper on 'regexpr' to extract the matches and captured groups from the match of a regular expression to a character vector. See re_match.

Match a regular expression to a character vector

Description

This function is a small wrapper on the regexpr base R function, to provide an API that is easier to use.

Usage

re_match(pattern, text, ...)

Arguments

Details

Currently only the first occurence of the pattern is used.

Value

A character matrix of the matched (sub)strings. The first column is always the full match. This column is named .match. The result of the columns are capture groups, with appropriate column names, if the groups are named.

Examples

dates <- c("2016-04-20", "1977-08-08", "not a date", "2016",
  "76-03-02", "2012-06-30", "2015-01-21 19:58")
isodate <- "([0-9]{4})-([0-1][0-9])-([0-3][0-9])"
re_match(text = dates, pattern = isodate)

# The same with named groups
isodaten <- "(?<year>[0-9]{4})-(?<month>[0-1][0-9])-(?<day>[0-3][0-9])"
re_match(text = dates, pattern = isodaten)

Extract all matches of a regular expression

Description

This function is a thin wrapper on the gregexpr base R function, to provide an API that is easier to use. It is similar to re_match, but extracts all matches, including potentially named capture groups.

Usage

re_match_all(pattern, text, ...)

Arguments

Value

A list of character matrices. Each list element contains the matches of one string in the input character vector. Each matrix has a .match column that contains the matching part of the string. Additional columns are added for capture groups. For named capture groups, the columns are named.