Program to Compare two Strings in R

Last Updated : 24 Apr, 2025

String comparison is a common operation where two strings are compared in a case sensitive manner and check whether they are equal or not. In this article you will learn the various way in which you can compare two string in R language.

Concepts Related to the Topic :

String Comparison: Comparison of two strings and check whether they are equal or not.
Equality Operators (==): It is used to compare two string for equality and inequality.
Case Sensitivity: In R language programming strings are considers as case-sensitive by default. There are functions like tolower() or toupper() to make case-insensitive comparison.
tolower(): tolower() is the function to convert the string to lower case.
toupper(): toupper() is the function to convert string to upper case.
identical(): indentical() is function to compare two string and true or false according to the input string.
grepl(): grepl() is function to compare two string partially.

Strings

A collection of character variables make up a string. There is only one dimension to the cast of characters. In R, a string is defined as one or more letters surrounded in a pair of matching single or double quotes. In R programming, strings are used to represent textual material and can include special characters, digits, and spaces. " is used to denote an empty string. R Strings are always kept in double-quoted form in storage. Single quotes may appear inside of a double-quoted string. Single quotes are not permitted in single-quoted strings. In a similar vein, double quotations cannot be enclosed in double quotes.

Steps Needed :

Define the two strings you want to compare.
Use a comparison operator (== or !=) to compare the strings.
Use functions like tolower() or toupper() for case-insensitive comparisons.
Use grepl() for partial comparision.
Use identical() for string comparision.
Use if condition and print the result.

Case-sensitive comparison

In this example we have compare two string in case sensitive.

# Define two strings(str1 and str2)
String_1 <- "geeksforgeeks"
String_2 <- "GEEKSFORGEEKS"

# Conditional if statement to check whether string are equal or not
if (String_1 == String_2) {
  cat("The strings are equal")
} else {
  cat("The strings are not equal")
}

Output:

The strings are not equal

Since the case are not equal for both the strings, so output is false i.e. "The strings are not equal".

Case-Insensitive comparison

In this example we have compare two string in case Insensitive.

# Define two strings(str1 and str2)
String_1 <- "geeksforgeeks"
String_2 <- "GEEKSFORGEEKS"

# tolower() to convert string to lower case
ans <- tolower(String_1) == tolower(String_2)

# Conditional if statement to check whether ans is true or not
if (ans) {
  cat("The strings are equal")
} else {
  cat("The strings are not equal")
}

Compare two strings uising identical()

There is another method to compare string using identical() function. An identical function is used in R to check whether two R objects are equal/ identical or not.

# Define two strings(str1 and str2)
String_1 <- "geeksforgeeks"
String_2 <- "GEEKSFORGEEKS"

# identical() to compare two string and return true or false
ans <- identical(tolower(String_1),tolower(String_2))

# Conditional if statement to check whether ans is true or not
if (ans) {
  cat("The strings are equal")
} else {
  cat("The strings are not equal")
}

Compare two strings partially using grepl()

The word “grepl” stands for “grep logical”. The grepl() function in R simply searches for matches in characters or sequences of characters present in a given string.

# Define two strings(str1 and str2)
String_1 <- "geeks for geeks"
String_2 <- "for"

# grepl() function to check if "for" is present in  or not "geeks for geeks"
ans <- grepl(String_2,String_1)

# Conditional if statement to check whether ans is true or not
if (ans) {
  cat("The strings are equal")
} else {
  cat("The strings are not equal")
}