This book contains reproductions of the code samples from Joel Grus’ book Data Science from Scratch in Python (the original language), Scala, and Clojure. A multi-language implementation will make the concepts stick better, as well as portray relevant distinctions between the languages if the code is written in an idiomatic way.
This project is licensed under the Unlicense (just like the original code samples from the book), which means it is in the public domain.