Regular Expressions in R Programming Language
# R offers built-in support for regular expressions.
# Here are some examples of common regexp-related tasks in R.
# This tests whether a pattern matches a string.
match <- grepl("p([a-z]+)ch", "peach")
print(match)
# For other regexp tasks, we'll use the stringr package
# which provides a consistent interface for working with regular expressions.
library(stringr)
# Create a regular expression pattern
r <- "p([a-z]+)ch"
# Test if the pattern matches a string
print(str_detect("peach", r))
# Find the first match for the regexp
print(str_extract("peach punch", r))
# Find the start and end indexes for the match
print(str_locate("peach punch", r))
# Extract both the whole-pattern matches and the submatches
print(str_match("peach punch", r))
# Find all matches for a regexp
print(str_extract_all("peach punch pinch", r))
# Replace subsets of strings with other values
print(str_replace("a peach", r, "<fruit>"))
# Transform matched text with a given function
print(str_replace_all("a peach", r, toupper))
# Compile a regular expression for repeated use
r_compiled <- str_c("p([a-z]+)ch")
print(r_compiled)
# Use the compiled regexp
print(str_extract_all("peach punch pinch", r_compiled))
This R code demonstrates various regular expression operations using both base R functions and the stringr
package, which provides a more consistent interface for working with regular expressions in R.
Here’s a breakdown of the operations:
We use
grepl()
from base R to test if a pattern matches a string.We load the
stringr
package for more advanced regex operations.str_detect()
is used to test if a pattern matches a string.str_extract()
finds and returns the first match for the regexp.str_locate()
returns the start and end indexes of the first match.str_match()
extracts both the whole-pattern matches and submatches.str_extract_all()
finds all matches for a regexp.str_replace()
replaces subsets of strings with other values.str_replace_all()
with a function argument transforms matched text.We use
str_c()
to create a compiled regular expression pattern.
Note that R doesn’t have a direct equivalent to Go’s regexp.Compile()
or regexp.MustCompile()
. In R, regular expressions are typically used directly as strings, and any “compilation” is handled internally by the functions that use them.
To run this R script, save it to a file (e.g., regular_expressions.R
) and run it using:
$ Rscript regular_expressions.R
For a complete reference on R regular expressions, check the documentation for the stringr
package and the base R regex functions (?regex
in R).