[R] peculiar matrices

[Gabor Grothendieck]

The reference manual of 2.2.0 says in section
2.2 that "Matrices and arrays are simply vectors
with the attribute dim and optionally dimnames."

Now earlier in section 2.1 it discusses vectors
and I think that that is where the confusing part lies.
Section 2.1 starts out saying that "Vectors
can be thought of as contiguous cells containing
homogeneous data." and that "R has six basic
('atomic') vector types: logical, integer, real,
complex, string (or character) and raw".   There
is no inkling yet that this is an incomplete
thought.

Its only later in the section that we find out that
atomic vectors are only one sort of vector: "Lists
are vectors, and the basic vector types are
referred to as atomic vectors where it is
necessary to exclude lists."

I think this section should be rewritten to
clearly state up front that there are atomic
vectors and generic vectors and then define each
of these.


On 10/21/05, Ben Bolker <bolker at ufl.edu> wrote:
>
> As far as I can tell from reading The Fine Documentation
> (R Language Definition and Intro to R), matrices are supposed
> to be of homogeneous types.  Yet giving matrix() an inhomogeneous
> list seems to work, although it produces a peculiar object:
>
> v = list(1:3,4,5,"a")
> m = matrix(v,nrow=2)
> m
>
>     [,1]      [,2]
> [1,] Integer,3 5
> [2,] 4         "a"
>
>
> m[1,]
>
> [[1]]
> [1] 1 2 3
>
> [[2]]
> [1] 3
>
>  (this is R 2.1.1, running under Linux)
>  Should there be a check/error? Or is this just analogous to
> the joke about going to the doctor and saying "it hurts when
> I do this", and the doctor saying "well then, don't do that"?
>
>  Ben Bolker
>
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