Check whether a given file exists

Check whether a given file exists

check.file.exists(
  file,
  failure.message = paste0("Sorry, but I cannot find the file \"", file,
    "\" in your current working directory."),
  success.message = paste0("Great, I have found the file \"", file, "\"!"),
  ps = get.ps(),
  part = NULL,
  ...
)