Introduction to Regular Expressions in R

Regular expressions (regex) allow you to match and manipulate text patterns efficiently. In this lesson, you'll learn the basics of using regex in R.

Using grep() to Find Patterns

The grep() function searches for patterns in a vector.

text <- c('apple', 'banana', 'cherry')
grep('a', text)

Using grepl() to Check for Patterns

The grepl() function returns TRUE or FALSE if a pattern is found.

grepl('a', text)

Extracting Matches with regexpr()

The regexpr() function locates the first occurrence of a pattern in a string.

regexpr('an', 'banana')

Using gsub() for Replacement

The gsub() function replaces all occurrences of a pattern in a string.

gsub('a', '@', 'banana')

Using sub() for First Match Replacement

The sub() function replaces only the first occurrence of a pattern.

sub('a', '@', 'banana')

Using str_extract() for Pattern Extraction

The str_extract() function from stringr extracts matched patterns.

library(stringr)
str_extract('abc123', '\d+')

Using str_replace_all()

The str_replace_all() function replaces multiple matches using stringr.

library(stringr)
str_replace_all('banana', 'a', '@')

Summary

In this lesson, you learned:

• How to find patterns using grep() and grepl().
• How to extract and replace patterns in text.
• How to use stringr for advanced regex operations.