Package Installation Issues

[mickremedi]

There are a couple of plotting packages that have an issue installing because they all seem to depend on either the 'xml2' or 'XML' packages.

The errors appeared when trying to use the pacman package to load the packages:
cowplot
plotROC
tidyverse

Also, I think it's a good idea to substitute the 'install.packages' functions with the pacman 'p_load' function in the rmd files like you had done in some cases so that we don't have to constantly try to reinstall packages.

@rexdouglass @tlscherer

[mickremedi]

I found a solution that solves the problem for any computer running MacOS. It seems that in the new updates to the operating system, '/usr/include' isn't being used anymore for system headers which breaks some packages that rely on it. To fix this issue:

1. Open up Finder
2. On the top bar click on the 'Go' dropdown
3. Click on 'Go to Folder...' and type this path '/Library/Developer/CommandLineTools/Packages' which should send you to a folder with a single .pkg file
4. Double click this file

You'll go through an installation process that would download about 200mb of headers onto your system including those that 'xml2' and 'XML' need to install.