[Rd] Bug in xy.coords() or documentation error?

[Gabor Grothendieck]

I think the docs have been changed for the next vesion
of R.

On 1/21/06, Gavin Simpson <gavin.simpson at ucl.ac.uk> wrote:
> On Sat, 2006-01-21 at 13:12 -0500, Gabor Grothendieck wrote:
> > This was discussed just recently.   This is a design
> > error but the maintainers claim there are no cases of
> > interest where it matters.
>
> Thanks Gabor,
>
> I must have missed that discussion whilst I was on vacation. If what you
> say was the outcome of that discussion, it still means that the
> documentation for xy.coords is in error, as you may *not* provide a
> single argument 'x'.
>
> If the intention is to keep the current behaviour - which is fine - then
> the documentation should be changed, perhaps along the lines of:
>
>    x, y: the x and y coordinates of a set of points. Alternatively, a
>          single object 'x' can be provided if 'y = NULL' is also
>          supplied.
>
> 'object' might not be correct here - is a formula an 'object'?
>
> Cheers,
>
> Gav
>
> >
> > On 1/21/06, Gavin Simpson <gavin.simpson at ucl.ac.uk> wrote:
> > > Hi,
> > >
> > > I noticed the following problem with xy.coords() in R 2.2.1-patched
> > > (version info at the foot of this email) and R 2.3.0 unstable
> > > (subversion no: r37123):
> > >
> > > > xy.coords(x = matrix(1:20, ncol = 2))
> > > Error in xy.coords(x = matrix(1:20, ncol = 2)) :
> > >        argument "y" is missing, with no default
> > > > xy.coords(x = matrix(1:20, ncol = 2), y = NULL)
> > > $x
> > >  [1]  1  2  3  4  5  6  7  8  9 10
> > >
> > > $y
> > >  [1] 11 12 13 14 15 16 17 18 19 20
> > >
> > > $xlab
> > > [1] "[,1]"
> > >
> > > $ylab
> > > [1] "[,2]"
> > >
> > > And:
> > >
> > > > xy.coords(x = data.frame(x = 1:10, y = 1:10))
> > > Error in xy.coords(x = data.frame(x = 1:10, y = 1:10)) :
> > >        argument "y" is missing, with no default
> > > > xy.coords(x = data.frame(x = 1:10, y = 1:10), y = NULL)
> > > $x
> > >  [1]  1  2  3  4  5  6  7  8  9 10
> > >
> > > $y
> > >  [1]  1  2  3  4  5  6  7  8  9 10
> > >
> > > $xlab
> > > [1] "x"
> > >
> > > $ylab
> > > [1] "y"
> > >
> > > ... for example.
> > >
> > > ?xy.coords states:
> > >
> > >    x, y: the x and y coordinates of a set of points. Alternatively, a
> > >          single argument 'x' can be provided.
> > >
> > > Given that, I would have thought the above examples would have worked
> > > without explicitly passing y = NULL to xy.coords(). However, ?xy,coords
> > > later states:
> > >
> > >    If 'y' is 'NULL' and 'x' is a
> > >
> > > and the examples all illustrate the use of NULL passed as y.
> > >
> > > Is this a documentation error and a single argument x is not allowed, or
> > > is this a bug in the code? Either way, ?xy.coords contradicts itself as
> > > one would expect to be able to pass only x given the statement above.
> > >
> > > If this is a bug in the code, a potential workaround appears to be to
> > > change the first line of xy.coords from:
> > >
> > >   if (is.null(y)) {
> > >
> > > to
> > >
> > >   if (missing(y) || is.null(y)) {
> > >
> > > but I haven't tested this on anything other than my two examples.
> > >
> > > I will file a bug report if my observation is correct - but given all
> > > the erroneous bug reports lately, I thought I'd try my luck here where
> > > an error on my part would not cause the maintainers of the bug tracker
> > > any extra work.
> > >
> > > > version
> > >         _
> > > platform i686-pc-linux-gnu
> > > arch     i686
> > > os       linux-gnu
> > > system   i686, linux-gnu
> > > status   Patched
> > > major    2
> > > minor    2.1
> > > year     2006
> > > month    01
> > > day      18
> > > svn rev  37123
> > > language R
> > > > sessionInfo()
> > > R version 2.2.1, 2006-01-18, i686-pc-linux-gnu
> > >
> > > attached base packages:
> > > [1] "methods"   "stats"     "graphics"  "grDevices"
> > > [5] "utils"     "datasets"  "base"
> > >
> > > All the best,
> > >
> > > Gav
> > >
> > > --
> > > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
> > > Gavin Simpson                     [T] +44 (0)20 7679 5522
> > > ENSIS Research Fellow             [F] +44 (0)20 7679 7565
> > > ENSIS Ltd. & ECRC                 [E] gavin.simpsonATNOSPAMucl.ac.uk
> > > UCL Department of Geography       [W] http://www.ucl.ac.uk/~ucfagls/cv/
> > > 26 Bedford Way                    [W] http://www.ucl.ac.uk/~ucfagls/
> > > London.  WC1H 0AP.
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> > >
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> > >
> --
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> Gavin Simpson                     [T] +44 (0)20 7679 5522
> ENSIS Research Fellow             [F] +44 (0)20 7679 7565
> ENSIS Ltd. & ECRC                 [E] gavin.simpsonATNOSPAMucl.ac.uk
> UCL Department of Geography       [W] http://www.ucl.ac.uk/~ucfagls/cv/
> 26 Bedford Way                    [W] http://www.ucl.ac.uk/~ucfagls/
> London.  WC1H 0AP.
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
>
>