[Rd] is.matrix

[Wacek Kusnierczyk]

hadley wickham wrote:
> On Tue, Nov 11, 2008 at 1:42 PM, Wacek Kusnierczyk
> <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
>   
>> hadley wickham wrote:
>>     
>>>> |  is.matrix| returns |TRUE| if |x| is a matrix and has a |dim <dim.html>|
>>>> attribute of length 2) and |FALSE| otherwise
>>>>
>>>>         
>>> That's confusing!  In what situations is x a matrix but does not have
>>> a dim attribute?
>>>
>>>
>>>       
>> x = matrix(1,1,1)
>> dim(x) = c(1,1,1)
>>     
>
> I think you meant
> dim(x) <- c(3, 1)
>
> You created a 1 x 1 x 1 array.
>   

i know, that's precisely what i wanted.  this is a simple 3d structure,
yet is(x) reveals it is a matrix.  that was the point.

some further observations:

x = as.list(1:2)
is(x)
# x is a list

dim(x) = 2
is.list(x)
# sure
is(x)
# not so sure any more -- a matrix?

vQ