R Function which tries to load packages and installs those packages that are not installed already.

load_or_install_packages.R

#' Load or install packages
#' 
#' It tries to install the specified packages multiple (deafault is 10) times.
#'
#' @param packages character vector of packages which should be loaded or installed if they are not already.
#' @param recursive_depth Argument that is used for selecting how many times the installation should be tried. 
#'   Defaults to 10. Not intended to be changed.
#'
#' @return
#' @export
#'
#' @examples
#' load_or_install(c('XML', 'jsonlite', 'data.table', 'glue'))
#'
load_or_install <- function(packages, recursive_depth = 10, lib_path = .libPaths()[length(.libPaths())]) {
  # try to load libraries, install those missing
  # packages_are_installed contains TRUE/FALSE for loaded/not installed packages
  packages_are_installed <- sapply(packages, function(package){
    if(!require(package, character.only = TRUE)) {
      install.packages(package, repos = 'https://cloud.r-project.org', lib = lib_path)
      # require returns TRUE for loaded packages, FALSE for those not.
      require(package, character.only = TRUE)
    } else {
      # return TRUE because the package is loaded (the first require())
      TRUE
    }
  })
  # We recursively install packages that did not install the previous time
  if (!all(packages_are_installed)) {
    packages_to_install <- packages[!packages_are_installed]
    if (recursive_depth > 0) {
      load_or_install(packages_to_install, recursive_depth - 1)
    } else {
      stop(paste0('ERROR: Even after many (10) tries could not install packages: ', paste(packages_to_install, collapse = ", "), '.'))
    }
  }
}


load_or_install(packages = c('XML', 'jsonlite', 'data.table', 'glue'))