Bug in xy.coords() or documentation error?
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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