Overview
re is an R package designed to simplify working with regular expressions by providing a set of functions similar to Python’s re module. The package includes utilities for compiling regular expressions with specific flags, checking for matches, escaping special characters, and more. By emulating the functionality and naming conventions of Python’s re module, re aims to make regex operations in R more intuitive and accessible, especially for those familiar with Python.
Installation
You can install the re package directly from GitHub.
# Install devtools if you haven't already
install.packages("devtools")
# Install re package from GitHub
devtools::install_github("pythonicr/re")Getting Started
Basic Usage
Here are some examples demonstrating how to use the functions provided by the re package.
Compile a Regular Expression with Specific Flags
The re_compile function compiles a regular expression pattern with specified flags. This step is optional as flags and patterns can be provided for any of the functions.
library(re)
# Compile a pattern with case-insensitive matching
pattern <- re_compile("^abc", IGNORECASE = TRUE)
# Compile a pattern with multi-line matching (abbreviations are based on Python's re package)
pattern <- re_compile("end$", M = TRUE)
pattern <- re_compile("end$", MULTILINE = TRUE)
# Compile a pattern with DOTALL flag
pattern <- re_compile("a.b", DOTALL = TRUE)Check if a String Contains a Regular Expression
The re_contains function checks whether a specified pattern is found within each element of a character vector.
# Check if strings contain a pattern
re_contains(pattern, "Abcdef")
#> [1] FALSE
re_contains("xyz$", "hello world xyz")
#> [1] TRUEEscape Special Characters
The re_escape function escapes all special characters in a regular expression string.
Extract All Occurrences of a Pattern in a String
The re_findall function extracts all occurrences of a specified pattern from each element of a character vector.
# Extract all words from a string
pattern <- re_compile("\\b\\w+\\b")
re_findall(pattern, "This is a test.")
#> [[1]]
#> [1] "This" "is" "a" "test"
re_findall("\\d+", "123 abc 456")
#> [[1]]
#> [1] "123" "456"Match a Pattern Against the Entire String
The re_fullmatch function checks whether each element of a character vector fully matches a specified pattern.
# Check for full matches in a string
pattern <- re_compile("\\d{3}-\\d{2}-\\d{4}")
re_fullmatch(pattern, "123-45-6789")
#> [[1]]
#> [1] "123-45-6789"
re_fullmatch("123-45-6789", "123-45-6789 and more")
#> [[1]]
#> [1] NAMatch a Pattern at the Start of a String
The re_match function checks whether each element of a character vector matches a specified pattern at the start.
# Check for matches at the start of a string
pattern <- re_compile("\\d{3}")
re_match(pattern, "123abc")
#> [[1]]
#> [1] "123"
re_match("abc", "xyzabc")
#> [[1]]
#> [1] NASearch for a Pattern in a String
The re_search function searches for occurrences of a specified pattern within each element of a character vector.
# Search for a pattern in a string
pattern <- re_compile("\\d+")
re_search(pattern, "abc 123 xyz")
#> [[1]]
#> [1] "123"
re_search("\\bword\\b", "A sentence with the word.")
#> [[1]]
#> [1] "word"Split a String by a Regular Expression Pattern
The re_split function splits each element of a character vector into substrings based on a specified pattern.
# Split strings based on a pattern
pattern <- re_compile("\\s+")
re_split(pattern, "Split this string")
#> [[1]]
#> [1] "Split" "this" "string"
re_split("\\W+", "Split,with!punctuation.morestuff", maxsplit = 2)
#> [[1]]
#> [1] "Split" "with" "punctuation.morestuff"Substitute Occurrences of a Pattern in a String
The re_sub function replaces all occurrences of a specified pattern in each element of a character vector with a replacement string.
# Substitute patterns in a string
pattern <- re_compile("\\d+")
re_sub(pattern, "number", "Replace 123 with text.")
#> [1] "Replace number with text."
re_sub("\\s+", "-", "Split and join")
#> [1] "Split-and-join"