On Fri, 17 Oct 2003, Liaw, Andy wrote:
> Somehow R creates `a' as a matrix with 0 rows and 5 columns. I don't know
> how crossprod() or other linear algebra functions deals with such a
> degenerate matrix.
>
> I'd suggest R Core to add checks for strictly positive dimensions in such
> functions.
Yes. There usually are, which is why the matrix multiplication version
works
> (Also, I find it strange that A[1,] is a vector, but A[numeric(0),] is a 0x5
> matrix...)
>
Why? A[1,] is a 1x5 matrix, ie, a column vector, so it makes sense for it
to decay to a vector. A[numeric(0),] is not a vector, so it stays a
matrix.
-thomas
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