[Rd] class(<matrix>) |--> c("matrix", "arrary") [was "head.matrix ..."]

[William Dunlap]

arrays and matrices have a numeric dims attribute, vectors don't.  If
statements lead to bad code.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Nov 15, 2019 at 1:19 PM Abby Spurdle <spurdle.a using gmail.com> wrote:

> > > And indeed I think you are right on spot and this would mean
> > > that indeed the implicit class
> > > "matrix" should rather become c("matrix", "array").
> >
> > I've made up my mind (and not been contradicted by my fellow R
> > corers) to try go there for  R 4.0.0   next April.
>
> I'm not enthusiastic about matrices extending arrays.
> If a matrix is an array, then shouldn't all vectors in R, be arrays too?
>
> > #mockup
> > class (1)
> [1] "numeric" "array"
>
> Which is a bad idea.
> It contradicts the central principle that R uses "Vectors" rather than
> "Arrays".
> And I feel that matrices are and should be, a special case of vectors.
> (With their inheritance from vectors taking precedence over anything else).
>
> If the motivation is to solve the problem of 2D arrays, automatically
> being mapped to matrices:
>
> > class (array (1, c (2, 2) ) )
> [1] "matrix"
>
> Then wouldn't it be better, to treat 2D arrays, as a special case, and
> leave matrices as they are?
>
> > #mockup
> > class (array (1, c (2, 2) ) )
> [1] "array2d" "matrix" "array"
>
> Then 2D arrays would have access to both matrix and array methods...
>
> Note, I don't want to enter into (another) discussion on the
> differences between implicit class and classes defined via a class
> attribute.
> That's another discussion, which has little to do with my points above.
>
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