Week 9

Iteration

Published

March 5, 2026

Modified

March 17, 2026

Topics

Introduce statistical modeling and learn how to fit a simple linear regression model and run a t-test in R
Learn how to use broom functions to tidy up statistical model output
Learn about for loops
Understand how to apply a function to a list
Learn how to iterate over a list using map() functions from the purrr package

Functions of the Week
- Please upload to Sakai your FOTW presentation by 7 am of the day you are presenting.
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 in OneDrive folder BSTA_526_W26_class_materials_public.
For today’s class, make sure to download to your computer the folder called part9.
Open RStudio by double-clicking on the project file called BSTA_526_W26_class_materials_public.Rproj in the main OneDrive folder.

Note: The link to the slides version of the class notes is not working. Please see the OneDrive folder for the html of the slides.


Part	OneDrive folder	Slides	Webpage
9

R4DS book:
- for loops: 27.5
- Iteration: Chapter 26
  - Section 26.2: Modifying multiple columns is on using the across() function, such as in mutate(across()), which we’ve already covered. You can skip this section if you like.
  - Section 26.3 Reading multiple files introduces purrr::map() which is new to us. Make sure to read this section.
Learn to purrr from Rebecca Barter’s blog. This is a nice non-technical introduction to purrr and the various map variants.

purrr tutorial by Jenny Bryan
- I recommend the Core purrr lessons
Advanced R book (we’ve graduated from the R4DS book!) by Hadley Wickham
- Functionals: Chapter 9
  - This chapter covers purrr in detail. It’s the most technical of the suggested readings.

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