Lecture 2

Overview

• Identify the importance of graphics in data analysis
• Define the layered grammar of graphics
• Practice generating layered graphics using ggplot2
• Learn best practices for coding style in R

Before class

• Make sure your setup is completed and works as expected! See the “Before class” from Lecture 1 for details, and let us know (via Ed Discussion) if you have questions!
• Check Homework 1

Readings

Coding style:

• Chapter 4 “Workflow: code style” from “R for Data Science” 2nd Edition
• “The tidyverse style guide”: skim it for today, and refer back to it whenever you are unsure!

Grammar of Graphics and ggplot2:

• Required: read “Chapter 1 Data visualization” from “R for Data Science” 2nd Edition. To be able to follow today’s lecture, you need to read this chapter!
• Recommended: read Hadley Wickham A Layered Grammar of Graphics – the “pre-print” version of the article can be downloaded for free. This article is optional, but I encourage you to skim through it to familiarize yourself with the theory behind the Grammar of Graphics. See especially section 3 “Components of the Layered Grammar” and section 4 “A Hierarchy of Defaults.” Understanding the logic of the Grammar of Graphics will make it much easier to apply it in R

Additional resources on ggplot2 (check these out whenever you need to make plots for this class or later on):

• ggplot2 Cheat Sheet
• ggplot2 Documentation
• ggplot2: Elegant Graphics for Data Analysis, 2nd Edition by Hadley Wickham. Excellent resource for learning the intricacies of ggplot2
• R Graphics Cookbook, 2nd edition by Winston Chang. A practical guide with 150 examples to generate quality statistical graphics based on the data you wish to present
• Tufte, Edward R. The Visual Display of Quantitative Information. Classic book on statistical graphics and visualization design.
• Healey, Kieran. Data Visualization: A Practical Guide. An applied introduction to graphical design with lots of code examples.

Class materials

Run the code below in your console to download today’s materials: usethis::use_course("css-materials/grammar-of-graphics")¹