Scanning a project folder for R packages to install

Several tools attempt to address the package installation problem, including packrat and checkpoint. Both these tools have internal methods to scan folders for packages that are used in the project, but these methods aren't exposed in a convenient way.

This little function uses a non-exported method from the packrat package to scan for required packages. The function will also optionally install these packages, after first comparing to what's already on your system.

scan_and_install <- function(path, 
                             lib = .libPaths()[1], 
                             repos = getOption("repos"), 
                             install = FALSE)
  {
  stopifnot(require("packrat"))
  pkgs <- packrat:::appDependencies(path)
  to_install <- pkgs[!(pkgs %in% unname(installed.packages()[, "Package"]))]
  if (install && length(to_install)){
    install.packages(to_install, lib = lib, repos = repos)
  }
  to_install
}

To list the required packages in a project, try:

scan_and_install("path/to/project/")

And to also install the missing packages, add the argument install = TRUE:

scan_and_install("path/to/project/", install = TRUE)