# The intersect() function in R

rtip
Author

Steven P. Sanderson II, MPH

Published

July 28, 2023

# Introduction

Welcome to another exciting blog post where we delve into the world of R programming. Today, we’ll be discussing the `intersect()` function, a handy tool that helps us find the common elements shared between two or more vectors in R. Whether you’re a seasoned R programmer or just starting your journey, this function is sure to become a valuable addition to your toolkit.

# Syntax

The `intersect()` function in R has a simple and intuitive syntax:

``intersect(x, y)``

Here, `x` and `y` are the input vectors for which we want to find the common elements. The function returns a new vector containing the intersection of `x` and `y`.

# Examples

Let’s dive into some practical examples to understand how the `intersect()` function works and see its power in action.

## Example 1: Finding Common Elements

Suppose we have two vectors, `vec1` and `vec2`, with some elements in common. We want to find those common elements:

``````vec1 <- c(1, 3, 5, 7, 9)
vec2 <- c(2, 4, 6, 8, 5, 10)

common_elements <- intersect(vec1, vec2)
common_elements``````
``[1] 5``

### Explanation

In this example, we have two vectors, `vec1` and `vec2`. The `intersect()` function takes these two vectors as input and identifies the common element between them, which is `5`. The function returns a new vector with only the common element.

## Example 2: Removing Duplicates

The `intersect()` function can also be used to remove duplicates from a single vector:

``````repeated_vec <- c(1, 2, 3, 4, 1, 2, 5, 6)

unique_elements <- intersect(repeated_vec, repeated_vec)
unique_elements``````
``[1] 1 2 3 4 5 6``

### Explanation

In this example, we have a vector `repeated_vec` with some duplicate elements. By using `intersect()` with the same vector twice, the function effectively removes all duplicates, giving us a new vector with only unique elements.

## Example 3: Empty Intersection

If the input vectors have no common elements, the `intersect()` function will return an empty vector:

``````vec3 <- c(11, 22, 33)
vec4 <- c(44, 55, 66)

empty_intersection <- intersect(vec3, vec4)
empty_intersection``````
``numeric(0)``

### Explanation

In this case, `vec3` and `vec4` have no elements in common. Thus, the `intersect()` function returns an empty numeric vector (`numeric(0)`).

## Example 4: Using Strings

Here is a final example using strings:

``intersect(c("apple", "banana", "cherry"), c("banana", "cherry", "grape"))``
``[1] "banana" "cherry"``

# Encouragement

Now that you’ve grasped the power of the `intersect()` function, I encourage you to explore and experiment with it further. Try using this function with different types of vectors, such as character vectors or logical vectors. Challenge yourself to find unique applications for this function in your projects.

Remember, exploring the functions and capabilities of R on your own is a fantastic way to strengthen your programming skills and deepen your understanding of the language. Happy coding!

# Conclusion

In this blog post, we’ve introduced the `intersect()` function in R, which helps us find the common elements between two or more vectors. We explored its syntax and provided several examples to illustrate its functionality. Now you have a valuable tool in your R toolkit to work with sets of data and identify shared elements efficiently. Keep coding and have fun exploring the endless possibilities of R!