Test if Character is in String in R (2 Examples)
This tutorial illustrates how to identify whether a character is contained in a string in the R programming language.
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Let’s dive right into the examples:
Creation of Example Data
First, we’ll have to create some example data:
my_x <- "XXXXAXXX" # Create example string my_x # Print string # "XXXXAXXX"
Have a look at the previous RStudio console output. It shows that our example string contains a sequence of the alphabetical letter X and in between is an A.
Example 1: Check If String Contains Character Using grepl() Function
In Example 1, I’ll show how to test for certain characters in our string using the grepl function. For this, we have to specify the character for which we want to search (i.e. A) and the name of our character string (i.e. my_x):
grepl("A", my_x) # Apply grepl function # TRUE
The RStudio console returned the logical value TRUE after running the previous R code. This means that the character A is contained in our string.
Let’s apply the grepl function to a character that is not in our string:
grepl("B", my_x) # Non-existing character # FALSE
As you can see, the RStudio console returned FALSE, i.e. the letter B is not in our string.
Example 2: Check If String Contains Character Using str_detect() Function of stringr Package
Alternatively to the grepl function shown in Example 1, we can also use the str_detect function provided by the stringr add-on package.
If we want to use the functions of the stringr package, we first have to install and load stringr:
install.packages("stringr") # Install & load stringr library("stringr")
Now, we can use str_detect as shown below:
str_detect(my_x, "A") # Apply str_detect function # TRUE
The str_detect function also returns a logical value, i.e. TRUE.
Video, Further Resources & Summary
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