From: Robin Hankin <r.hankin_at_noc.soton.ac.uk>

Date: Wed 05 Oct 2005 - 20:19:43 EST

Date: Wed 05 Oct 2005 - 20:19:43 EST

Hi

I need X = solve(t(H) %*% Ainv %*% H) %*% t(H) %*% Ainv %*% d

It is possible to rewrite X in the recommended crossprod way:

X <- solve(quad.form(Ainv, H), crossprod(crossprod(Ainv, H), d))

where quad.form() is a little function that evaluates a quadratic form:

jj <- crossprod(M, x) return(drop(crossprod(jj, jj)))}

**QUESTION:
**
how to calculate

in the recommended crossprod way? (I don't want to take a transpose because t() is expensive, and I know that %*% is slow).

-- Robin Hankin Uncertainty Analyst National Oceanography Centre, Southampton European Way, Southampton SO14 3ZH, UK tel 023-8059-7743 ______________________________________________ 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 Wed Oct 05 20:34:04 2005

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