[Rd] is.matrix

[Wacek Kusnierczyk]

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)
is.matrix(x)
# no
is("matrix", x)
# no
is(x)
# hm...

following the last, there would be a situation in which an object is a
matrix (per is(...)) and has a dim attribute of length != 2, but is a
matrix (per is.matrix(...) and is("matrix", ...), consistently with the
docs).

(the redundant "vector" in is(x) could probably be removed?)

vQ