Re: [Rd] Wish there were a "strict mode" for R interpreter. What about You?

From: Hadley Wickham <>
Date: Sat, 09 Apr 2011 16:31:07 -0500

On Sat, Apr 9, 2011 at 2:51 PM, Paul Johnson <> wrote:
> Years ago, I did lots of Perl programming. Perl will let you be lazy
> and write functions that refer to undefined variables (like R does),
> but there is also a strict mode so the interpreter will block anything
> when a variable is mentioned that has not been defined. I wish there
> were a strict mode for checking R functions.
> Here's why. We have a lot of students writing R functions around here
> and they run into trouble because they use the same name for things
> inside and outside of functions. When they call functions that have
> mistaken or undefined references to names that they use elsewhere,
> then variables that are in the environment are accidentally used. Know
> what I mean?
> dat <- whatever
> someNewFunction <- function(z, w){
>   #do something with z and w and create a new "dat"
>   # but forget to name it "dat"
>    lm (y, x, data=dat)
>   # lm just used wrong data
> }
> I wish R had a strict mode to return an error in that case. Users
> don't realize they are getting nonsense because R finds things to fill
> in for their mistakes.
> Is this possible?  Does anybody agree it would be good?

> library(codetools)
> checkUsage(someNewFunction)

<anonymous>: no visible binding for global variable ‘y’
<anonymous>: no visible binding for global variable ‘x’
<anonymous>: no visible binding for global variable ‘dat’

Which also picks up another bug in your function ;)


Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University

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