R ggplot2 Error: stat_count() must not be used with a y aesthetic (Example)

In this article you’ll learn how to handle the error message “stat_count() must not be used with a y aesthetic.” in the R programming language.

Table of contents:

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Example Data, Packages & Basic Graphic

As a first step, we’ll need to create some example data:

data <- data.frame(x = LETTERS[1:5],    # Example data
                   y = 5:1)
data                                    # Print data
#   x y
# 1 A 5
# 2 B 4
# 3 C 3
# 4 D 2
# 5 E 1

The previous output of the RStudio console reveals the structure of our example data: It consists of five rows and two columns. The variable x contains the groups of our data and the variable y contains the corresponding values.

If we want to plot our data with the ggplot2 add-on package, we also have to install and load ggplot2:

install.packages("ggplot2")             # Install ggplot2 package
library("ggplot2")                      # Load ggplot2 package

Example 1: ggplot2 Barchart with Default Specification in geom_bar() Function

This Example explains how to reproduce the error message “stat_count() must not be used with a y aesthetic.”.

This error typically occurs when we try to draw a barplot with the geom_bar function. Have a look at the following R code:

ggplot(data, aes(x, y)) +               # Draw barchart with ggplot2 package
  geom_bar()
# Error: stat_count() must not be used with a y aesthetic.

As you can see, the RStudio console returned the error “stat_count() must not be used with a y aesthetic.”.

The reason for this is that we have tried to use the default specifications of the geom_bar function AND we have specified a y-variable within the aes() function.

By default, the geom_bar function uses the argument stat = “count”, which is not possible when we are specifying a y-variable as well.

Next, I’ll show how to fix this…

Example 2: ggplot2 Barchart with stat = “identity” in geom_bar() Function

The syntax below explains how to fix the error message “stat_count() must not be used with a y aesthetic.”. For this, we have to explicitly specify the stat argument within the geom_bar function to be equal to “identity”:

ggplot(data, aes(x, y)) +               # Draw barchart with ggplot2 package
  geom_bar(stat = "identity")

Figure 1 shows the output of the previous R code – A ggplot2 barplot.

Video & Further Resources

If you need more information on the topics of this article, you might want to watch the following video of my YouTube channel. I’m explaining the R codes of this article in the video instruction.

In addition, you may have a look at the related articles that I have published on this website. A selection of articles on topics such as counting, labels, and graphics in R can be found below.

• Add Count Labels on Top of ggplot2 Barchart
• Introduction to the ggplot2 Package
• ggplot2 Plot in Script is not Displayed
• Fixing Warning & Error Messages in R
• Plots in R
• The R Programming Language

Summary: This article explained how to deal with the error “stat_count() must not be used with a y aesthetic.” in R programming. In case you have any further questions, please let me know in the comments section. Besides that, don’t forget to subscribe to my email newsletter for updates on new articles.