R scoping: disallow global variables in function

Question

Is there any way to throw a warning (and fail..) if a global variable is used within a R function? I think that is much saver and prevents unintended behaviours

Answer 1

You can check whether the variable's name appears in the list of global variables. Note that this is imperfect if the global variable in question has the same name as an argument to your function.

if (deparse(substitute(var)) %in% ls(envir=.GlobalEnv))
    stop("Do not use a global variable!")

The stop() function will halt execution of the function and display the given error message.