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

Duncan Murdoch murdoch@dunc@n @end|ng |rom gm@||@com
Fri Jan 22 16:50:37 CET 2021

I think it's always difficult and sometimes impossible to take an 
existing session and convert it to the vanilla state, but it's very easy 
to run a new instance of R from an existing one.

So instead of a clearws() function, I'd suggest a "runInVanilla" 
function, that takes some code as input, starts up a vanilla session and 
collects the output.

This is quite similar to what reprex::reprex does, maybe not different 
at all.

Duncan Murdoch

On 22/01/2021 10:37 a.m., J C Nash wrote:
> 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.

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