Convert String to Lowercase in R

R comes with two functions to convert strings to lowercase: tolower() and casefold() functions. The tolower() function in R converts a string to lowercase. This function takes a single argument, which is the string to be converted. In this guide, we will show how to convert string to lowercase in R.

Using tolower() Function to Convert String to Lowercase

In this method, we will use the tolower() function to convert string to lowercase in R.

Syntax

tolower(x)

Arguments

• x = string to be converted

Example 1: Using tolower() to Convert a Single String to Lowercase

# converting to lowercase
tolower("HELLO WORLD!")

Output

[1] "hello world!"

Example 2: Using tolower() to Convert a Vector of Strings to Lowercase

# creating a vector
x = c("HELLO", "WORLD!")
# converting to lowercase
tolower(x)

Output

[1] "hello" "world!"

Example 3: Using tolower() to Convert a Column of a Data Frame

# creating a data frame
df = data.frame(x = c('Fruit', 'Vegetable', 'Dairy'), y = c('APPLE', 'POTATO','CURD'))
df
# converting column y to lowercase
tolower(df$y)

Output

x y
1 Fruit APPLE
2 Vegetable POTATO
3 Dairy CURD

[1] "apple" "potato" "curd"

In the above example, we used the $ sign to extract the column y from the data frame df.

Using casefold() Function to Convert String to Lowercase

Unlike the tolower() function, the casefold() function takes two arguments.

Syntax

casefold(x, upper=FALSE)

Arguments

1. x = string to be converted
2. upper = If TRUE then all characters are converted to uppercase. By default, it is FALSE, which converts the characters to lowercase.

Example 1: Using casefold() to Convert a Single String to Lowercase

# converting to lowercase
casefold("JUSTICE LEAGUE", upper=FALSE)

Output

[1] "justice league"

Example 2: Using casefold() to Convert a Vector of Strings to Lowercase

# creating a vector
x = c("JUSTICE", "LEAGUE")
# converting to lowercase
casefold(x,upper=FALSE)

Output

[1] "justice" "league"

Example 3: Using casefold() to Convert a Column of a Data Frame

# creating a data frame
df = data.frame(x = c('Dominos', 'McDonalds', 'Starbucks'), y = c('PIZZA', 'BURGERS','COFFEE'))
df
# converting to lowercase
tolower(df$y)

Output

x y
1 Dominos PIZZA
2 McDonalds BURGERS
3 Starbucks COFFEE

[1] "pizza" "burgers" "coffee"