We decided to write this book as a freely available open source document for a number of reasons. Firstly, we hope this book will be a living document that naturally evolves over time. If you find any errors in the book or want to make a suggestion on how to improve it, please open an issue on the GitHub site or even better click on the edit button in the navigation bar at the top of this page and issue a pull request (only available on the web version of this book). Please note that this book uses a Contributor Code of Conduct. By contributing to this book, you agree to abide by its terms. If you feel like contributing to the book, please get in touch, we’d be happy to hear from you. If you want to take a peek at all the code behind the book visit the book GitHub repo. Secondly, the release of the bookdown package by Yihui Xie has made it incredibly easy to collaboratively write, update and maintain this book using RMarkdown, RStudio and GitHub. Without the bookdown package this book wouldn’t exist in its current format. Lastly, R is not just software, it’s also a wonderful open community with many thousands of contributors all working to make R even easier to learn and use. This is our small contribution.