How to Check if a Vector Contains a Given Element in R

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You can use the following methods to check if a vector contains a given element in R:

Method 1: Check if Vector Contains Element

'some_element' %in% my_vector

Method 2: Find Position of First Occurrence of Element

match('some_element', my_vector)

Method 3: Find Position of All Occurrences of Element

which('some_element' == my_vector)

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

Example 1: Check if Vector Contains Element

The following code shows how to check if ‘Andy’ exists in a given vector:

#create vector
my_vector <- c('Andy', 'Bert', 'Chad', 'Doug', 'Bert', 'Frank')

#check if vector contains 'Andy'
'Andy' %in% my_vector

[1] TRUE

The output displays TRUE since the element ‘Andy’ does exist in the vector.

However, suppose we check if ‘Arnold’ exists in the vector:

#create vector
my_vector <- c('Andy', 'Bert', 'Chad', 'Doug', 'Bert', 'Frank')

#check if vector contains 'Arnold'
'Arnold' %in% my_vector

[1] FALSE

The output displays FALSE since the element ‘Arnold’ does not exist in the vector.

Example 2: Find Position of First Occurrence of Element

The following code shows how to find the position of the first occurrence of ‘Bert’ in a given vector:

#create vector
my_vector <- c('Andy', 'Bert', 'Chad', 'Doug', 'Bert', 'Frank')

#find first occurrence of 'Bert'
match('Bert', my_vector)

[1] 2

The output displays 2 since the element ‘Bert’ occurs first in position 2 of the vector.

And the following code shows how to find the position of the first occurrence of ‘Carl’ in the vector:

#create vector
my_vector <- c('Andy', 'Bert', 'Chad', 'Doug', 'Bert', 'Frank')

#find first occurrence of 'Carl'
match('Carl', my_vector)

[1] NA

The output displays NA since the element ‘Carl’ never occurs in the vector.

Example 3: Find Position of All Occurrences of Element

The following code shows how to find all occurrences of ‘Bert’ in a given vector:

#create vector
my_vector <- c('Andy', 'Bert', 'Chad', 'Doug', 'Bert', 'Frank')

#find all occurrences of 'Bert'
which('Bert' == my_vector)

[1] 2 5

The output displays 2 and 5 since these are the positions in the vector where ‘Bert’ occurs.

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