Plot Mean in ggplot2 Barplot in R (Example)
This page explains how to create a ggplot2 barchart that shows the mean of each group in the R programming language.
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Example Data, Add-On Packages & Basic Graph
To start with, we’ll need to create some example data:
data <- data.frame(group = letters[1:3], # Create example data value = 1:12) data # Print example data
Have a look at the previous table. It shows that our example data contains twelve rows and two columns.
In order to apply the functions of the ggplot2 package, we also have to install and load ggplot2:
install.packages("ggplot2") # Install & load ggplot2 library("ggplot2")
Now, we can draw our data in a ggplot2 barchart as shown below. In this first plot, we’ll use the default specifications of the geom_bar function, i.e. the sum of each group.
ggplot(data, aes(group, value)) + # ggplot2 barplot with sum geom_bar(stat = "identity")
In Figure 1 it is shown that we have created a ggplot2 bargraph with sums.
Example: Plot Mean in ggplot2 Barchart Using position, stat & fun Arguments
This example shows how to draw the mean in a ggplot2 barplot.
For this, we have to specify three arguments within the geom_bar function:
- position = “dodge”
- stat = “summary”
- fun = “mean”
Have a look at the following R code:
ggplot(data, aes(group, value)) + # ggplot2 barplot with mean geom_bar(position = "dodge", stat = "summary", fun = "mean")
By executing the previous R code we have created Figure 2, i.e. a ggplot2 barchart showing the mean of each category or factor level.
Video, Further Resources & Summary
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