ProjectTemplate is Not Meant to Help You Build an R Package

ProjectTemplate is not designed to help you write R packages. If you're looking to do that, you should start by looking at the package.skeleton() function provided by the utils package. In the future, we hope that there will be better tools for building packages in R, but the ProjectTemplate team probably won't be building those sort of tools anytime soon.

If it's not clear to you why ProjectTemplate isn't meant to help you write your own package, here are some important ways in which a statistical analysis project differs from a package: