A function for installing R packages if you don't already have them installed.

try_install_load.R

# Only install packages when you can't find them
try.install.load = function(pack.name, libpath=.libPaths()[1]) {
  t = try(library(pack.name, lib.loc = libpath, character.only = TRUE))
  if("try-error" %in% class(t)) {
    install.packages(pack.name, lib = libpath)
    library(pack.name, lib.loc = libpath, character.only = TRUE)
  }
}