Week 3

Errors, data manipulation with dplyr, ggplot: themes, colors, facets

Topics

Part 3:

• Getting help with errors
• Data manipulation with dplyr package
  • pipe (%>% or |>)
  • Rows: arrange, filter
  • Columns: select, tidyselect
• Saving data files
• More ggplot
  • Themes, colors
  • Boxplots
  • Facets

Announcements

• TA’s office hours are Mondays 3:00-4:00 pm (Michael Daily) via Webex. Webex link is on main course page of Sakai.
  
• Cascadia R Conf in June 26-27 this year. It will be held at OHSU in RLSB. This is a great conference to meet other R enthusiasts in the area and learn more about what they are working on.

Class materials

• Class materials in OneDrive folder BSTA_526_W26_class_materials_public.
• For today’s class, make sure to download to your computer the folder called part3.
• Open RStudio by double-clicking on the project file called BSTA_526_W26_class_materials_public.Rproj in the main OneDrive folder.

Part	OneDrive folder	Slides	Webpage
3

Readings

Required

ggplot2

• R4DS book
  • Chapter 1: Data visualization intro
  • Sections 9.1-9.3: Aesthetic mappings, geometric objects, facets
  • Section 11.5: ggplot themes

dplyr

• R4DS book sections 3.1-3.3 (skip 3.3.1, which will be covered in part 4), 12.3
• dplyr cheatsheet - one of the best references.
• Combining functions using the pipe operator, |> which is mostly equivalent to %>%; if you’re confused about |> or %>%, please read this.

Optional

ggplot2

If you are interested in learning more about ggplot:

• ggplot2 BERD workshop slides - lots more on different geoms and how to customize plots
• Themes to improve your ggplot figures by David Keyes is really helpful for learning how to do more styling.
• RStudio also publishes a ggplot cheat sheet that is really handy!
• Customizing ggplot2 Cheatsheet is also handy, because it organizes ggplot2 commands by task.
• Documentation for all ggplot features is available here.
• New ggplot options with the latest version 4 released in September 2025

janitor package

Take a look at the janitor vignette to learn more about functions include in the janitor package

Below are janitor functions being covered in part 3:

• clean_names()
• remove_empty()
• tabyl()

Post-class survey

• Please fill out the post-class survey to provide feedback. Thank you!
• Previous muddiest points and clearest points with responses are collected here.

Homework

• See OneDrive folder for homework assignment.
• HW 3 due on 01/29.

Recording

• In-class recording links are on Sakai. Navigate to Course Materials -> Schedule with links to in-class recordings.