Replace Specific Characters in String in R (4 Examples)


This article illustrates how to exchange a certain character pattern within a string in the R programming language.

Table of contents:

Let’s dive right in…


Example Data

Let’s first define some example data:

x <- "xxxxyxxyxaaaaaay"           # Create example character string
x                                 # Print character string
# "xxxxyxxyxaaaaaay"

As you can see based on the previous output of the RStudio console, our example data is a character string containing of the letters x, y, and a.


Example 1: Replace All Occurrences of Specific Character in String

In this Example, I’ll show how to replace all appearances of the letter y by the character pattern NEW. For this, we can use the gsub function as shown below:

gsub("y", "NEW", x)               # Applying gsub
# "xxxxNEWxxNEWxaaaaaaNEW"

As you can see based on the previous output, our updated character string contains the character pattern NEW instead of the alphabetical letter y.


Example 2: Replace First Occurrence of Specific Character in String

Example 2 shows how to use the sub function to exchange only the first occurrence of the letter y in our character string. Have a look at the following R code:

sub("y", "NEW", x)                # Applying sub
# "xxxxNEWxxyxaaaaaay"

As you have seen in this and the previous example, the gsub function is used to replace all occurrences of a character patter and the sub function is used to replace only the first occurrence.


Example 3: Replace All Occurrences Using str_replace_all Function of stringr Package

The stringr package is a powerful add-on package for the manipulation of character strings in R.

For that reason, I want to show in Examples 3 and 4, how to use the functions of the stringr package to replace certain characters in strings.

If we want to use the commands & functions of the stringr package, we first need to install and load stringr:

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

Now, we can apply the str_replace_all function of the stringr package to replace all occurrences of the letter y.

str_replace_all(x, "y", "NEW")    # Applying str_replace_all
# "xxxxNEWxxNEWxaaaaaaNEW"

The previous output is exactly the same as in Example 1.


Example 4: Replace First Occurrence Using str_replace Function of stringr Package

In this Section, I’ll show how to exchange only the first appearance of a character in a string using the str_replace of the stringr package.

str_replace(x, "y", "NEW")        # Applying str_replace
# "xxxxNEWxxyxaaaaaay"

This time, the output is exactly the same as in Example 2.


Video, Further Resources & Summary

If you need more info on the examples of this page, you may watch the following video of my YouTube channel. I show the content of this article in the video:


The YouTube video will be added soon.


In addition to the video, you may have a look at some of the other articles on my homepage. I have published several other tutorials about related topics such as extracting data and character strings.


Summary: This article illustrated how to replace characters in strings in R programming. Let me know in the comments section below, if you have additional questions and/or comments. Furthermore, don’t forget to subscribe to my email newsletter in order to get updates on new articles.


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