R: How to Check if Character is in String

You can use the following methods to check if a character is in a string in R:

Method 1: Check if Character is in String Using Base R

grepl(my_character, my_string, fixed=TRUE)

Method 2: Check if Character is in String Using stringr Package

library(stringr) 

str_detect(my_string, my_character)

The following examples show how to use each method in practice.

Example 1: Check if Character is in String Using Base R

The following code shows how to check if “Doug” exists in a particular string in R:

#define character to look for
my_character <- "Doug"

#define string
my_string <- "Hey my name is Douglas"

#check if "Doug" is in string
grepl(my_character, my_string, fixed=TRUE)

[1] TRUE

Since “Doug” does exist in the string, the grepl() function returns TRUE.

Suppose we instead check if “Steve” exists in the string:

#define character to look for
my_character <- "Steve"

#define string
my_string <- "Hey my name is Douglas"

#check if "Steve" is in string
grepl(my_character, my_string, fixed=TRUE)

[1] FALSE

Since “Steve” does not exist in the string, the grepl() function returns FALSE.

Example 2: Check if Character is in String Using stringr Package

The following code shows how to use the str_detect() function from the stringr package to check if the string “Doug” exists in a particular string:

library(stringr)

#define character to look for
my_character <- "Doug"

#define string
my_string <- "Hey my name is Douglas"

#check if "Doug" is in string
str_detect(my_string, my_character)

[1] TRUE

The str_detect() function returns TRUE since “Doug” is in the string.

Note that we can also use the following syntax to check if several characters exist in the string:

library(stringr)

#define vector of characters to look for
my_characters <- c("Doug", "Steve", "name", "He")

#define string 
my_string <- "Hey my name is Douglas"

#check if each character is in string
str_detect(my_string, my_characters)

[1]  TRUE FALSE  TRUE  TRUE

From the output we can see: