R – Check If All Elements in a Vector are Equal

In this tutorial, we will look at how to check if all the elements in an R vector are equal with the help of some examples.

How to check if all vector elements are equal in R?

You can use a combination of the length() and the unique() functions in R to check if all the elements in a vector are equal or not. The following is the syntax –

# check if all elements in vector are equal
length(unique(vec)) == 1

Here, we first apply the unique() function to keep only the distinct values from the vector and then use the length() function to compute the length of this unique values vector.

If the length is equal to 1, we can say that all the elements in the vector are equal. If it were not the case, then the length of the unique value vector would be greater than 1.

Examples

Let’s now look at some examples of checking for equality among all elements in a vector.

Using length() and unique() to check check if all vector elements are equal

Let’s create a vector of length four having the same element in all the indices and apply the method from above.

# create a vector
vec <- c(7, 7, 7, 7)
# check if all elements in vec are equal
print(length(unique(vec))==1)

Output:

[1] TRUE

We get TRUE as the output. This means that the unique values vector has length 1 which indicates that all the values in the vector vec are equal.

Using var() to check if all vector elements are equal

For numeric vectors, you can also use the var() function in R to check if all the values are equal or not.

The var() function returns the variance in the vector. The idea is, that if the variance of a vector is 0 then all the elements inside the vector are the same.

Let’s look at an example. We’ll use the same input vector as above.

# create a vector
vec <- c(7, 7, 7, 7)
# check if all elements in vec are equal
print(var(vec)==0)

Output:

[1] TRUE

We get TRUE as the output indicating that all the values in the vector are equal.

Note that this method will not work if your vector has non-numeric values. For example, let’s test it on a character vector.

# create a vector
vec <- c('a', 'a', 'a', 'a')
# check if all elements in vec are equal
print(var(vec)==0)

Output:

Warning message in var(vec):
“NAs introduced by coercion”
[1] NA

We get NA as the output and a warning. This is because we’re trying to compute the variance of a vector with non-numeric values.

Using a combination of the length() and the unique() function, however, will work irrespective of the type of values the vector has.

# create a vector
vec <- c('a', 'a', 'a', 'a')
# check if all elements in vec are equal
print(length(unique(vec))==0)

Output:

[1] TRUE

We get TRUE as the output.

You might also be interested in –

• Remove Duplicates From a Vector in R
• R – Count Distinct Values in a Vector
• How to add two vectors in R?