From: Andres Legarra <alegarra_at_neiker.net>

Date: Tue 23 Aug 2005 - 20:30:30 EST

Date: Tue 23 Aug 2005 - 20:30:30 EST

Hello,

I am calculating this thing with vectors (b) and matrices (G,P):
b'G/sqrt(b'Pb)

where the denominator is a quadratic form and therefore always a scalar.

In Scilab, it is quite simple:

b'*G/sqrt(b'*P*b)

However, in R, the denominator is an (1x1)matrix and R claims it is non
conformable and I have to use drop() or as.numeric(). Like this:

*> b = 1:2
**> G=diag(1,2)
*

> P=diag(2,2)

> (t(b)%*%G) / drop( sqrt( t(b)%*%P%*%b ) )

[,1] [,2]

[1,] 0.3162278 0.6324555

So far, so good. My problem is solved. However I found a little bit annoying
that R is not so "clever" as to realize that b'Pb can be interpreted as a
scalar. I wonder :

would it be worth considering the implementation in R of
"recycling 1x1 matrix to scalars if appropriate"?
Just to leave the question on the ground...

Regards,

Andres

-- Andres Legarra NEIKER Apdo. 46 Vitoria-Gasteiz 01080 Spain -- -- Andres Legarra Albizu NEIKER Apdo. 46 Vitoria-Gasteiz 01080 Spain phone: +34 945 121323 fax: +34 945 281422 e-mail: alegarra@neiker.net -- ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Tue Aug 23 20:34:46 2005

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