Overlay Histogram with Fitted Density Curve in Base R & ggplot2 Package (2 Examples)
In this tutorial you’ll learn how to fit a density plot to a histogram in the R programming language.
Table of contents:
- Introduction of Example Data
- Example 1: Histogram & Density with Base R
- Example 2: Histogram & Density with ggplot2 Package
- Video, Further Resources & Summary
Let’s just jump right in!
Introduction of Example Data
In the examples of this R programming tutorial, we’ll use the following example data:
set.seed(18462) # Create example data data <- data.frame(x = round(rnorm(1000, 10, 10))) head(data) # Print example data # x # 1 6 # 2 7 # 3 14 # 4 4 # 5 -10 # 6 16
As you can see based on the output of the RStudio console, our example data contains only one numeric column. Now, let’s draw these data…
Example 1: Histogram & Density with Base R
Example 1 explains how to fit a density curve to a histogram with the basic installation of the R programming language. First, we need to use the hist function to draw a histogram:
hist(data$x, prob = TRUE) # Create histogram with Base R
Figure 1: Histogram Created with Base R.
lines(density(data$x), col = "red") # Overlay density curve
Figure 2: Histogram & Overlaid Density Plot Created with Base R.
Figure 2 illustrates the final result of Example 1: A histogram with a fitted density curve created in Base R.
Example 2: Histogram & Density with ggplot2 Package
Example 2 shows how to create a histogram with a fitted density plot based on the ggplot2 add-on package. First, we need to install and load ggplot2 to R:
install.packages("ggplot2") # Install & load ggplot2 library("ggplot2")
Now, we can use a combination of the ggplot, geom_histogram, and geom_density functions to create out graphic:
ggplot(data, aes(x)) + # ggplot2 histogram & density geom_histogram(aes(y = stat(density))) + geom_density(col = "red")
Figure 3: Histogram & Overlaid Density Plot Created with ggplot2 Package.
Figure 3 visualizes our histogram and density line created with the ggplot2 package. Note that the histogram bars of Example 1 and Example 2 look slightly different, since by default the ggplot2 packages uses a different width of the bars compared to Base R.
Video, Further Resources & Summary
Some time ago I have published a video on my YouTube channel, which illustrates the content of this tutorial. You can find the video below:
Furthermore, you might want to have a look at some of the related articles which I have published on my homepage.
- Create Histogram in Base R
- Create Kernel Density Plot in R
- Create ggplot2 Histogram in R
- Draw Multiple Overlaid Histograms with ggplot2 Package
- Draw Multiple Variables as Lines to Same ggplot2 Plot
- R Graphics Gallery
- The R Programming Language
In this tutorial, I illustrated how to combine histograms with probability on the y-axis and density plots in the R programming language. If you have additional questions or comments, let me know in the comments section below.