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

[Gabor Grothendieck]

This was discussed just recently.   This is a design
error but the maintainers claim there are no cases of
interest where it matters.


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
>
> --
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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
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