How to Smoothen a Line Chart Plot using ggplot2

Learn how to effectively smoothen your line chart plots in R with `ggplot2`. Troubleshoot common errors and enhance the clarity of your data visualizations!
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This video is based on the question https://stackoverflow.com/q/66140425/ asked by the user 'daves_ma' ( https://stackoverflow.com/u/15121932/ ) and on the answer https://stackoverflow.com/a/66140903/ provided by the user 'pascal' ( https://stackoverflow.com/u/14866122/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

Creating visually appealing and easily interpretable line charts is essential for data analysis. A line chart allows you to see trends over time, but sometimes the data can look a bit jagged or cluttered. When this happens, smoothing techniques can be employed to produce a cleaner, more coherent representation of your data. In this guide, we’ll walk through a common question: How can we smoothen a line chart plot using the ggplot2 package in R?

In our example, we’ll explore a specific error encountered while attempting to apply smoothing to a line chart, and we’ll provide step-by-step instructions on how to fix it.

Understanding the Problem

While working with the ggplot2 package, a user encountered an issue while trying to smoothen a line chart. They received the following error message:

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

This error indicates that the stat_smooth() function lacks the necessary aesthetic mappings for the x and y axes.

Solution

To resolve this issue, we need to ensure we properly define the x and y aesthetics for the smoothing function. In ggplot2, the stat_smooth() function is used to add a smoothed line to your plot. Here's how to do it correctly:

Step 1: Modify the stat_smooth() Function

Instead of calling stat_smooth() without empowering it with the necessary mappings, we should use the aes() function within stat_smooth() to set the aesthetics. This can be done in two ways:

For the first line of the plot, ARIS_TOP:

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

For the second line of the plot, SWI_001:

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

Step 2: Include Both Smoothing Lines (Optional)

If you want to include smoothing for both lines in your chart, you can simply add both lines in a row like this:

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

Full Code Example

Here’s how your full ggplot code should look after incorporating the smoothing lines:

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

Conclusion

By correctly mapping the aesthetics in the stat_smooth() function, you can effectively smooth out your line charts in R using ggplot2. This not only resolves the error message you encountered but also enhances the clarity and visual appeal of your plots. Now you can confidently create line charts that communicate your data trends effectively!

Happy plotting!