How to Find Location of Character in a String in R

by Tutor Aspire January 17, 2023

You can use the following methods to find the location of a character in a string in R:

Method 1: Find Location of Every Occurrence

unlist(gregexpr('character', my_string))

Method 2: Find Location of First Occurrence

unlist(gregexpr('character', my_string))[1]

Method 3: Find Location of Last Occurrence

tail(unlist(gregexpr('character', my_string)), n=1)

Method 4: Find Total Number of Occurrences

length(unlist(gregexpr('character', my_string)))

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

The following code shows how to find every location of the character “a” in a certain string:

#define string
my_string = 'mynameisronalda'

#find position of every occurrence of 'a'
unlist(gregexpr('a', my_string))

[1]  4 12 15

From the output we can see that the character “a” occurs in position 4, 12, and 15 of the string.

The following code shows how to find the location of the first occurrence of the character “a” in a certain string:

#define string
my_string = 'mynameisronalda'

#find position of first occurrence of 'a'
unlist(gregexpr('a', my_string))[1]

[1] 4

From the output we can see that the character “a” first occurs in position 4 of the string.

The following code shows how to find the location of the last occurrence of the character “a” in a certain string:

#define string
my_string = 'mynameisronalda'

#find position of last occurrence of 'a'
tail(unlist(gregexpr('a', my_string)), n=1)
[1] 15

From the output we can see that the last occurrence of the character “a” is in position 15 of the string.

The following code shows how to find the total number of occurrences of the character “a” in a certain string:

#define string
my_string = 'mynameisronalda'

#find total occurrences of 'a'
length(unlist(gregexpr('a', my_string)))
[1] 3

From the output we can see that the character “a” occurs 3 times in the string.

The following tutorials explain how to perform other common operations in R: