How to Find Location of Character in a String in R


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.

Method 1: Find Location of Every Occurrence

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.

Method 2: Find Location of First Occurrence

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.

Method 3: Find Location of Last Occurrence

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.

Method 4: Find Total Number of Occurrences

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.

Additional Resources

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

How to Concatenate Strings in R
How to Convert a Vector to String in R
How to Convert Character to Factor in R

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