[Rd] Question about colnames behavior
Martin Maechler
maechler at stat.math.ethz.ch
Mon Oct 3 15:04:00 CEST 2005
>>>>> "BDR" == Prof Brian Ripley <ripley at stats.ox.ac.uk>
>>>>> on Mon, 3 Oct 2005 09:44:47 +0100 (BST) writes:
BDR> On Mon, 3 Oct 2005, Martin Maechler wrote:
>>>>>>> "Erich" == Erich Neuwirth <erich.neuwirth at univie.ac.at>
>>>>>>> on Sun, 02 Oct 2005 09:39:36 +0200 writes:
>>
Erich> The following code
Erich> zzz<-1:10
Erich> dim(zzz)<-10
Erich> rownames(zzz)
Erich> colnames(zzz)
>>
Erich> yields NULL for the rownames and colnames calls.
Erich> Let us set rownames
>>
Erich> rownames(zzz)<-1:10
>>
Erich> Now rownames(zzz) returns the expected result, but colnames(zzz)
Erich> produces an error:
Erich> Error in dn[[2]] : subscript out of bounds
>>
Erich> So given a onedimensional structure the return behavior of colnames
Erich> is different depending on the fact if rownames are set or not.
>>
Erich> Should the behavior of colnames be changed to make the result
Erich> independent from this fact?
>>
>> yes, thank you, Erich.
>> It should give an error also in the 1st case which is
>> BTW identical to
>> zzz <- array(1:10)
BDR> Not according to my reading of the help, which says
>> The extractor functions try to do something sensible for any
>> matrix-like object 'x'. If the object has 'dimnames' the first
>> component is used as the row names, and the second component (if
>> any) is used for the col names.
BDR> and reading on, I think it should give NULL in both cases. You could
BDR> argue that a 1D array is not `matrix-like', but that seems a narrow
BDR> interpretation (especially as rownames does work for such arrays).
I was lead to my conclusion by the same help page, reading
>> Arguments:
>>
>> x: a matrix-like R object, with at least two dimensions for 'colnames'.
from which I concluded an error was appropriate for 'colnames'
when 'x' doesn't have two dimensions.
If we adopt your proposal (NULL in any case), we should
definitely also fix that paragraph...
Martin
More information about the R-devel
mailing list