[Rd] is.matrix
Wacek Kusnierczyk
Waclaw.Marcin.Kusnierczyk at idi.ntnu.no
Tue Nov 11 20:55:04 CET 2008
Daniel Høyer Iversen wrote:
>> That's confusing! In what situations is x a matrix but does not have
>> a dim attribute?
>>
>
> That was my point. I don't find it logical that
> is.matrix(a) gives FALSE but
> is.matrix(t( t(a) )) gives TRUE.
>
that's a different story, because t() performs an implicit cast from
vector to matrix, so you have
t(vector) -> matrix
t(matrix) -> matrix
t(t(vector)) -> matrix
interestingly,
x = 1:2
dim(x) = 2
adds "matrix" to is(x), but it is still not is.matrix(x) (consistently
with the docs).
> I also think it would be more logical that
> a=c(1,1,2)
> dim(a) gives 3 1 instead of NULL,
>
well, it might give 3 1 1, or 3 1 1 1, or ..., which all could be
considered logical.
i think dim(x) giving just 3 would be fine.
vQ
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