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

From: Duncan Murdoch <murdoch.duncan_at_gmail.com>
Date: Sat, 09 Apr 2011 21:12:48 -0400

On 11-04-09 7:02 PM, Spencer Graves wrote:

> On 4/9/2011 2:31 PM, Hadley Wickham wrote:
>> On Sat, Apr 9, 2011 at 2:51 PM, Paul Johnson<pauljohn32_at_gmail.com>   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 ;)
>
>         Is this run by "R CMD check"?  I've seen this message.
>
>
>         "R CMD check" will give this message sometimes when I don't feel
> it's appropriate.  For example, I define a data object ETB in a package,
> then give that as the default in a function call like
> f(data.=ETB){if(missing(data.))data(ETB);  data.}.  When I run "R CMD
> check", I get "no visible binding for global variable 'ETB'", even
> though the function is tested and works during R CMD check.

What is ETB? Your code is looking for a global variable by that name, and that's what codetools is telling you.

Duncan Murdoch



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