Data Analysis with R: The Big Picture - This book is almost finished, and I’ve used it for courses. It’s may eventually be expanded into a more computational and up-to-date textbook called Data Science Workflow with R and the tidyverse.

A Systematic Guide to Mathematical Statistics - This is a long-term project, but early drafts of some sections are posted below.

Visualizing Linear Models - This textbook introduces the theory of linear models while connecting it deeply to functional analysis and probability theory. Throughout the text, drawings demonstrate how the material can be understood using intuition from Euclidean space. (A draft including several chapters will be posted soon.)