2.6 Additional infrastructure
When building some robust R packages, you may need additional software infrastructure. To save yourself the hassle of running into this problem later on, I’d also suggest the following installations (although feel free to skip those for now if you feel like you’ve done enough system administration for one sitting):
On Windows: Install Rtools. Download the appropriate Rtools.exe executable file for your version of R here: https://cran.r-project.org/bin/windows/Rtools/
On OS X: Install Xcode, Apple’s development environment, which should be available in the App Store.