[R] Why is rm(list=ls()) bad practice?

[J C Nash]

Thanks Duncan for a clear argument about the "why".

The suggestion of R --vanilla started a train of thought that one could do something like

 clearws <- function(){ # Try to clear workspace
   tmp <- readline("Are you sure you want to clear the workspace? ")
   print(tmp)
   if ( substr(toupper(tmp),1,1) != "Y" ){
       return(0)
   }
   #  rm(tmp)
   tgt<-parent.env(environment())
   print(ls(tgt))
   rm(list = ls(tgt, all.names = TRUE),envir=tgt) #will clear all objects includes hidden objects.
   gc() #free up memrory and report the memory usage.
   # What should we return?
   # Can we offer interactive control?
   # How about packages?
 }

and call clearws() at the start of an example.

Contact me off-list if you have suggestions for improving this. I'd like to be able to preface
examples with such a function that would render the session "vanilla" but from inside. That means
removing packages that might have altered / replaced / masked standard functions. That might not
be possible, but the idea is attractive to me as someone who mostly uses R in tests of tools that
get used by others.

Best, JN


On 2021-01-21 6:05 p.m., Duncan Murdoch wrote:
> On 21/01/2021 5:20 p.m., J C Nash wrote:
>> In a separate thread Jeff Newmiller wrote:
>>> rm(list=ls()) is a bad practice... especially when posting examples. It doesn't clean out everything and it removes
>>> objects created by the user.
>>
>> This query is to ask
>>
>> 1) Why is it bad practice to clear the workspace when presenting an example?
>> I'm assuming here that people who will try R-help examples will not run them in the
>> middle of something else, which I agree would be unfortunates. 
> 
> I think that's exactly the concern.  I doubt it would have happened in this instance, but in other cases, people might
> copy and paste a complete example before reading it.  It's safer to say:  "Run this code in a clean workspace:", rather
> than cleaning it out yourself.
> 
> Duncan Murdoch
> 
> 
> However, one of the
>> not very nice aspects of R is that it is VERY easy to have stuff hanging around (including
>> overloaded functions and operators) that get you into trouble, and indeed make it harder
>> to reproduce those important "minimal reproducible examples".  This includes the .RData
>> contents. (For information, I can understand the attraction, but I seem to have been
>> burned much more often than I've benefited from a pre-warmed oven.)
>>
>> 2) Is there a good command that really does leave a blank workspace? For testing
>> purposes, it would be useful to have an assured blank canvas.
> 
> Yes, start R with
> 
>   R --vanilla
> 
> Duncan Murdoch
> 
>>
>> This post is definitely not to start an argument, but to try to find ways to reduce
>> the possibilities for unanticipated outcomes in examples.
>>
>> Cheers, JN
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>