## How to contribute changes, or make your own version

Perhaps your professor has assigned a portion of this text to your class, with the instruction to improve it. Do you see the edit button at the top of the screen (it looks like a little square with a pencil)? If you click on that, and you have an account on Github (and you’re signed in), you will grab a copy of this entire text that you can then edit. If you want, you can also make a pull-request to us, asking us to fold your changes into our textbook. We welcome these suggestions! Since this book has a creative-commons license, you are welcome to expand and build upon this as you wish, but do cite and link back to the original version.

Instructors can take a copy of this repository as well, and re-edit or recombine the text in whatever ways will serve their learning goals best. We knit the markdown together inside R Studio with the Bookdown package. References are kept in the bibtex format in a .bib file. (For more information, see the colophon below.)