Re: chol() dimnames

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Subject: Re: chol() dimnames
From: Prof Brian Ripley (ripley@stats.ox.ac.uk)
Date: Mon 27 Sep 1999 - 21:25:05 EST


Message-Id: <199909271125.MAA07858@toucan.stats.ox.ac.uk>

> Date: Mon, 27 Sep 1999 11:18:52 +0100 (BST)
> From: Jonathan Rougier <J.C.Rougier@durham.ac.uk>
> To: r-devel@stat.math.ethz.ch
> Subject: chol() dimnames
>
> Hi Everyone,
>
> Just a minor point, but could chol() be changed to include the dimnames of
> the original matrix? This will ensure that x and t(R) %*% R have the same
> dimnames, where R <- chol(x). So we just need to insert
>
> if (!is.null(dx <- dimnames(x)))
> dimnames(z$v) <- dx
>
> ahead of the return. Cheers, Jonathan.

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?

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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