The str_count() function from the package in R can be used to count the number of matches in a string.

This function uses the following syntax:

str_count(string, pattern = “”)

where:

• string: Character vector
• pattern: Pattern to look for

The following examples show how to use this function in practice

Example 1: Use str_count with One Pattern

The following code shows how to use the str_count() function to count the number of times the letter ‘a’ occurs in each element in a character vector:

library(stringr)

#create character vector
x <- c('Mavs', 'Cavs', 'Nets', 'Trailblazers', 'Heat')

#count number of times 'a' occurs in each element in vector
str_count(x, 'a')

[1] 1 1 0 2 1

Here’s how to interpret the output:

• The pattern ‘a’ occurs 1 time in ‘Mavs’
• The pattern ‘a’ occurs 1 time in ‘Cavs’
• The pattern ‘a’ occurs 0 times in ‘Nets’

And so on.

Note that str_count() is also case-sensitive, so a capital ‘A’ would return 0 for each element in the character vector.

Example 2: Use str_count with Multiple Patterns

The following code shows how to use the str_count() function to count the number of times the letter ‘a’ or the letter ‘s’ occurs in each element in a character vector:

library(stringr)

#create character vector
x <- c('Mavs', 'Cavs', 'Nets', 'Trailblazers', 'Heat')

#count number of times 'a' or 's' occurs in each element in vector
str_count(x, 'a|s')

[1] 2 2 1 3 1

Here’s how to interpret the output:

• The pattern ‘a’ or ‘s’ occurs 2 times in ‘Mavs’
• The pattern ‘a’ or ‘s’ occurs 2 times in ‘Cavs’
• The pattern ‘a’ or ‘s’ occurs 1 time in ‘Nets’

Note: The | symbol represents an “OR” operator in R.