How to Plot the Percentage of Factor Levels in R using ggplot2

This guide explains how to visualize the percentage of vehicle usage types in R with ggplot2. Learn step-by-step how to create an effective plot that highlights your data accurately.
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How to Plot the Percentage of Factor Levels in R using ggplot2

When working with categorical data, such as vehicle types and their usage, visualizing the distribution of each category can provide valuable insights. If you have a dataset that includes the different uses of vehicles and their respective counts, you may want to plot their percentages in a chart for better readability and understanding. In this post, we'll explore how to achieve this using R's ggplot2 library.

Understanding the Dataset

Let's consider an example where we have a dataset that records the use of vehicles:

Vehicle Uses: private, commercial, ambulance

Quantity: Number of vehicles for each use

The initial data structure looks like this:

[[See Video to Reveal this Text or Code Snippet]]

From this dataset, we can observe that the counts for each type of vehicle usage are as follows:

Private: 8 (2 + 6)

Commercial: 2 (1 + 1)

Ambulance: 4

The Challenge: Plotting the Percentages

The goal is to visualize the percentage of each type of vehicle use, but if you just count the records, the results might not reflect the true totals. One initial attempt might look like this:

[[See Video to Reveal this Text or Code Snippet]]

However, this would yield incorrect results because it counts the records instead of summing up the quantities. An attempt to adjust the code to use the quantity might look like this:

[[See Video to Reveal this Text or Code Snippet]]

Unfortunately, this will generate an error: Error: stat_count() can only have an x or y aesthetic.

The Solution: Use stat = "identity"

To correctly plot the percentages based on the quantity of vehicles, you need to use stat = "identity" within geom_bar(). This will tell ggplot2 that you want to use the actual values in the y aesthetic, rather than counting occurrences.

Here’s the Correct Code

Here’s how to properly implement it:

[[See Video to Reveal this Text or Code Snippet]]

What Each Part Means

aes(x = factor(use)): This defines that the x-axis will have the factor levels (vehicle uses).

geom_bar(stat = "identity", aes(y = (quantity)/sum(quantity))): This line tells ggplot2 to use the specified y-values directly, allowing you to plot the percentages relative to the total.

coord_flip(): This will flip the axes, making it easier to read the labels on the y-axis.

scale_y_continuous(labels = scales::percent): This formats the y-axis to display percentages.

Conclusion

By following these steps, you can effectively visualize the percentage of different vehicle uses in your dataset using ggplot2 in R. This method not only provides a clear representation of your data but also enhances your ability to communicate your findings. Happy plotting!