[Rd] Re: [R] abs() on data frames?!

[Prof Brian D Ripley]

Moved to R-devel, as this will get very technical!

On Tue, 26 Feb 2002, Henrik Bengtsson wrote:

> I might be wrong, but didn't the following work before R v1.4.x?
>
> R --vanilla
> > df <- data.frame(-10:10)
> > abs(df)
> Error in abs(df) : non-numeric argument to function
>
> I have tried this on both Rv1.4.1 on WinMe and Rv1.4.0 on Solaris 8. I
> regexp searched bugs.r-project.org on "abs" but I found nothing about this.
> I can't see why abs(df) shouldn't work when sqrt(df), log(df) etc works.

Both log and abs should be members of the group generic Math, and
Math.data.frame exists. In R sqrt is dispatched on that group, although I
don't see it documented as part of it,

But it looks like abs is being handled by the complex arithmetic section of
the code, as if it were Mod.

I do recall discussions of this long ago, but doubt if this has been
changed recently.  Indeed, the names.c file has

/* KH(1999/09/12)-> complex: {"abs", do_math1, 0, 1, 1, PP_FUNCALL}, */

I'll fix it in R-devel.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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