chol() dimnames

Jonathan Rougier Jonathan Rougier <>
Mon, 27 Sep 1999 13:02:39 +0100 (BST)

Hi Brian,

On Mon, 27 Sep 1999, Prof Brian Ripley wrote:

> This is a picky comment, but maybe we should try to get this spot on.

> (i) Suppose that the row and column names of x are different? Which should
> one use?
> (ii) I don't think that R has any obvious row names: effectively this is
> a linear transformation to a different and unamed basis for the space.
> I believe all one actually knows is that the colnames of R should be the
> colnames of x, if the row and column names of x match. However, the 
> prototype does preserve the names.  Should we just preserve the colnames?

I think your qualms would be answered if the attribution of dimnames was
only made in the event that x has matching row and column names.  Whether
just the column names should be preserved in this case is a moot point.
But you might imagine a cautious programmer wanting to be sure that the
row names of Q correspond with the row names of some other matrix A in the
calculation t(Q) %*% A.  Preserving the row names doesn't do any harm, and
it might just be helpful.

Cheers, Jonathan.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE

"[B]egin upon the precept ... that the things we see are to be 
 weighed in the scale with what we know"  (Meredith, 1879, The Egoist)

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