[R] columnwise multiplication?

[Prof Brian Ripley]

On Fri, 23 Jun 2006, Mu Tian wrote:

> Hi all,
>
> I'd like to do a multiplication between 2 matrices buy only want resulsts of
> cloumn 1 * column 1, column 2 * column 2 and so on.
>
> Now I do
>
> C <- diag(t(A) %*% B)
>
> Is there a bulit in way to do this?

If * here means vector inner product, colSums(A*B) which is a lot more 
efficient.

>
> Thank you.
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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