Week 3 Live Session (Fall 2026)

In this week 3 session we covered data visualization with {ggplot2}, starting with how to think about charts in terms of aesthetic properties. We answered participant questions on color versus fill, reordering bars, flipping bar charts, wrapping long labels and removing legends, and previewed the data viz exercise and next week's Quarto lesson.

You'll learn:

• How to format R code automatically on save with the Air extension, and how to turn on format on save in the settings
• How to describe a chart in terms of {ggplot2} aesthetic properties such as x, y and fill
• How to get a filled point with a different outline color by using shape = 21 in geom_point()
• How to reorder bars with reorder() or by turning a variable into a factor, and why arrange() does not change plot order
• How to adjust a flipped bar chart with hjust, change bar width, wrap long facet labels with str_wrap(), and remove a legend with legend.position = "none"

Resources mentioned:

• Air
• {ggplot2}
• Positron
• {stringr}
• {gapminder}
• {palmerpenguins}
• {tidyverse}
• {dplyr}
• {forcats}
• Quarto

Key moments:

• 04:52 Most confusing parts of {ggplot2} and how it differs from Excel
• 14:08 Demo of the Air extension for automatic code formatting
• 17:13 Tall versus wide code formatting discussion
• 20:49 Turning on format on save in user settings
• 22:07 Reading a New York Times chart as aesthetic properties
• 25:08 Single versus double equals signs and lowercase x and y
• 29:27 Color versus fill in geom_point() and shape = 21
• 35:25 Participant question on arrange() not changing plot order
• 37:52 Reordering bars with reorder() and factors
• 43:31 Flipping a bar chart and switching vjust to hjust
• 47:36 Wrapping long facet labels with str_wrap()
• 54:21 Removing a legend with legend.position