Group Factor Levels in R (Example)

In this R tutorial you’ll learn how to regroup factor levels of a factor vector or column.

The tutorial consists of this information:

You’re here for the answer, so let’s get straight to the R syntax:

Construction of Example Data

As the first step, we’ll have to create some exemplifying data:

x <- factor(c("a", "b", "a", "c", "c"))    # Create example factor
x                                          # Print example factor
# [1] a b a c c
# Levels: a b c

The previous output of the RStudio console shows that our example data is a factor vector with three different factor levels.

Example: Combine Factor Levels Using levels() Function

In this example, I’ll illustrate how to merge two factor levels into one category using the levels function in R.

Have a look at the following R code:

x_new <- x                                 # Duplicate example factor
levels(x_new) <- c("a", "b", "b")          # Regroup factor levels
x_new                                      # Print updated factor
# [1] a b a b b
# Levels: a b

As you can see based on the previous output of the RStudio console, we have created a new factor vector called x_new that contains only two factor levels. The factor level “c” was replaced by / combined with the factor level “b”.

Video & Further Resources

Do you need more info on the contents of this tutorial? Then you might watch the following video of my YouTube channel. In the video, I’m explaining the R codes of this article:

Furthermore, you might have a look at the related articles of my homepage. Please find a selection of articles below.

• droplevels R Example
• Reorder Levels of Factor without Changing Order of Values
• Keep Unused Factor Levels in ggplot2 Barplot
• Introduction to R Programming

In this R tutorial you have learned how to collapse factor levels of a factor vector.

Please note that it would be possible to apply the same R syntax to group a factor column of a data frame instead of a vector as well.

Let me know in the comments section, if you have any further questions.