>>>>> "DM" == Duncan Murdoch <murd...@stats.uwo.ca>
>>>>> on Fri, 12 Jun 2009 06:09:14 -0400 writes:
DM> On 11/06/2009 5:35 PM, Stavros Macrakis wrote:
>> A table without names displays like a vector:
>>
>> > unname(table(2:3)) [1] 1 1 1
>>
>> and preserves the table class (as with unname in
>> general):
>>
>> > dput(unname(table(2:3))) structure(c(1L, 1L), .Dim =
>> 2L, class = "table")
>>
>> Does that make sense? R is not consistent in its
>> treatment of such unname'd tables:
DM> One of the complaints about the S3 object system is that
DM> anything can claim to be of class "foo", even if it
DM> doesn't have the right structure so that foo methods
DM> work for it. I think that's all you're seeing here:
DM> you've got something that is mislabelled as being of
DM> class "table". The solution is "don't do that".
indeed!
>> In plot, they are considered erroneous input:
>>
>> > plot(unname(table(2:3))) Error in xy.coords(x, y,
>> xlabel, ylabel, log) : 'x' and 'y' lengths differ
>>
>> but in melt, they act as though they have names 1:n:
>>
>> > melt(unname(table(2:3))) indicies value 1 1 1 2 2 1
>>
>> (By the way, is the spelling error built into too much
>> code to be corrected?)
>>
>> -s
>>
>> PS What is the standard way of extracting just the
>> underlying vector? c(unname(...)) works -- is that what
>> is recommended?
DM> I would use as.numeric(), but I don't claim it's
DM> standard.
many months ago in a discussion about the use (and "misuse") of
c() for coercing arrays/matrices to (atomic) vectors, Brian
Ripley I think advertized the use of as.vector()
with which I strongly agree.
as.vector() here has the additional advantage of *not*
transforming integer into double.
Martin Maechler, ETH Zurich
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