Compare Two Vectors For Differences in R

Vectors are used to store one-dimensional data of the same type in R. In this tutorial, we will look at how to compare two vectors for differences in R. That is, for example, for vectors vec1 and vec2, we want the elements of vec1 that are not in vec2 and vice versa.

How to compare vectors for differences in R?

You can use the R setdiff() function to compare two vectors for differences in R. Pass the two vectors as arguments to the function.

The following is the syntax –

# unique elements of vec1 not in vec2
setdiff(vec1, vec2)

It returns the elements of the vector vec1 that are not in the vector vec2. That is, it essentially calculates the set difference vec1 - vec2. Note that the order of arguments is very important as the set difference vec1 - vec2 may not be the same as the set difference vec2 - vec1.

Alternatively, you can also use a combination of the ! operator and the %in% operator to select elements of vec1 that are not in vec2.

The following is the syntax –

# elements of vec1 not in vec2
vec1[!(vec1 %in% vec2)]

Let’s now look at some examples of using the above methods –

Vector difference using the setdiff() function

To get elements of the vector vec1 that are not in the vector vec2, pass vec1 as the first argument and vec2 as the second argument to the setdiff() function.

Let’s look at an example.

We will create two vectors (with some different elements) and compare them for differences using the setdiff() function.

# create two vector
vec1 <- c(1, 2, 2, 3, 4)
vec2 <- c(3, 4, 5, 6)
# elements of vec1 not in vec2
print(setdiff(vec1, vec2))

Output:

[1] 1 2

We get the elements of vec1 that are not in vec2. Also, notice that the returned vector does not contain any duplicates.

You can similarly get the elements of vec2 that are not in vec1. For this, pass vec2 as the first argument and the vec1 as the second argument to the setdiff() function.

# create two vector
vec1 <- c(1, 2, 2, 3, 4)
vec2 <- c(3, 4, 5, 6)
# elements of vec2 not in vec1
print(setdiff(vec2, vec1))

Output:

[1] 5 6

We get the elements of vec2 that are not in vec1.

Vector difference using ! and %in% operators

You can also use a combination of the ! and the %in% operators to filter the vector vec1 such that we get the elements of vec1 that are not in vec2.

Let’s look at an example. We will use the same vectors from the examples above.

# create two vector
vec1 <- c(1, 2, 2, 3, 4)
vec2 <- c(3, 4, 5, 6)
# elements of vec1 not in vec2
print(vec1[!(vec1 %in% vec2)])

Output:

[1] 1 2 2

We get elements of vec1 that are not in vec2. Notice, that here we also get the duplicate elements.

You can similarly get elements of vec2 that are not in vec1.

# create two vector
vec1 <- c(1, 2, 2, 3, 4)
vec2 <- c(3, 4, 5, 6)
# elements of vec2 not in vec1
print(vec2[!(vec2 %in% vec1)])

Output:

[1] 5 6

We get the element of vec2 that are not in vec1.

You might also be interested in –

• R – Check If All Elements in a Vector are Equal
• R – Count Distinct Values in a Vector
• Remove Duplicates From a Vector in R