str_extract Function in R (stringr Package)

In this tutorial, I’ll explain how to use the str_extract function to extract matching patterns from a character string in the R programming language.

Table of contents:

• Introduction of Example Data
• Example: Application of str_extract Function in R
• Video, Further Resources & Summary

Let’s start right away!

Introduction of Example Data

As a first step, we need to create an example string in R:

x <- "a simple example string"    # Create example character string

As you can see, our example character string simply contains the sentence “a simple example string”. Now, let’s apply the str_extract function of the stringr package to this string…

Example: Application of str_extract Function in R

First, we need to install and load stringr:

install.packages("stringr")       # Install stringr package
library("stringr")                # Load stringr package

After loading the R package, we can apply the str_extract function as follows:

str_extract(x, "exa")             # Apply str_extract function
# "exa"

Within the previous R code, we checked whether our example string x contains the pattern “exa”. Since our example string contains this character pattern, the str_extract returned the pattern to the RStudio console.

Let’s see what happens when we check for a non-existing pattern:

str_extract(x, "abc")             # Different pattern
# NA

Our example character string does not contain the character pattern “abc”. For that reason, the RStudio console returns NA.

Video, Further Resources & Summary

Do you need further information on the contents of this article? Then you could have a look at the following video of my YouTube channel. I’m explaining the R programming syntax of this post in the video instruction:

The YouTube video will be added soon.

Furthermore, you may want to have a look at the related tutorials of my website. A selection of tutorials about R programming can be found here:

• substr & substring Functions in R
• Extract First or Last n Characters from String in R
• nth, first & last Functions of dplyr Package
• R Functions List (+ Examples)
• The R Programming Language

In summary: In this R tutorial you learned how to extract matching patterns from a string with the str_extract function. If you have further comments or questions, don’t hesitate to let me know in the comments section below.