[R] stringsAsFactors param in expand.grid not working

[Martin Maechler]

>>>>> "RT" == Rolf Turner <r.turner at auckland.ac.nz>
>>>>>     on Tue, 19 May 2009 11:02:08 +1200 writes:

    RT> On 19/05/2009, at 10:20 AM, Steve Lianoglou wrote:

    >> Hi all,
    >> 
    >> I've (tried) to look through the bug tracker, and gmane-search the  
    >> R list to
    >> see if this has been mentioned before, and it looks like it hasn't.

Yes, thank you.

That's a bug on which we  (R-core) currently work.
More about this, and notably about Rolf's (.)*&^%)(&#%$)
proposal on the   R-devel  list.

Martin Maechler


    >> According to the R 2.9.0 release notes[1], the expand.grid function  
    >> should now
    >> take a stringsAsFactor=LOGICAL argument which controls whether or  
    >> not the
    >> function coerces strings as factors. While the parameter is indeed  
    >> in the
    >> function, a quick examination of the function's source shows that  
    >> the value
    >> of this argument is never checked, and all strings are converted to  
    >> factors
    >> as a matter of course.
    >> 
    >> The fix is pretty easy, and I believe only requires changing the  
    >> `if` check
    >> here:
    >> 
    >> if (!is.factor(x) && is.character(x))
    >> x <- factor(x, levels = unique(x))
    >> 
    >> To:
    >> 
    >> if (!is.factor(x) && is.character(x) && stringsAsFactors)
    >> x <- factor(x, levels = unique(x))
    >> 
    >> I can open a ticket regarding this issue and add this there if  
    >> necessary.
    >> 
    >> Thanks,
    >> -steve
    >> 
    >> [1] http://article.gmane.org/gmane.comp.lang.r.general/146891

    RT> While we're at it --- would it not make sense to have the  
    RT> stringsAsFactors
    RT> argument (once it's working) of expand.grid() default to options() 
    RT> $stringsAsFactors,
    RT> rather than to FALSE?

    RT> This would make no difference to me personally, since I set
    RT> options(stringsAsFactors=FALSE) in my .Rprofile.  But it might make some
    RT> people happier ....

    RT> cheers,

    RT> Rolf Turner

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