toupper()

toupper(x)

Returns: character · Updated March 13, 2026 · String Functions

strings case text base

toupper() converts character vectors to uppercase. This function is essential for case-normalization when comparing strings, cleaning user input, and standardising text data for analysis or storage.

Syntax

toupper(x)

Parameters

Parameter	Type	Default	Description
`x`	character	—	A character vector to convert

Examples

Basic usage

toupper("hello world")
# [1] "HELLO WORLD"

toupper("HeLLo WoRLd")
# [1] "HELLO WORLD"

Working with vectors

fruits <- c("Apple", "BANANA", "Cherry")
toupper(fruits)
# [1] "APPLE"  "BANANA" "CHERRY"

Practical applications

# Case-insensitive matching
names <- c("Alice", "BOB", "charlie")
target <- "ALICE"

toupper(names) == toupper(target)
# [1]  TRUE FALSE FALSE

Common Patterns

Case-insensitive table lookup

lookup_table <- c("yes" = 1, "no" = 2, "maybe" = 3)

user_response <- "YES"
lookup_table[toupper(user_response)]
# YES 
#   1

Data cleaning pipeline

raw_data <- data.frame(
  name = c("ALICE", "bob", "Charlie"),
  city = c("new york", "London", "PARIS")
)

raw_data$name <- toupper(raw_data$name)
raw_data$city <- toupper(raw_data$city)

# Result: all uppercase
#       name     city
# 1    ALICE  NEW YORK
# 2      bob    LONDON
# 3  CHARLIE    PARIS