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From Ted Dunning <>
Subject Re: [math] optimization refactoring
Date Mon, 23 Feb 2009 00:28:23 GMT
I think that Dmitri overstates his case a bit.

This multiplication in observation space works for some algorithms, not for
others.  Ordinary least squares regression is somewhat of an exception
here.  Logistic regression is a simple counter-example.

It is still useful to have a vector weight and it helps users.  It may be
useful in some situations to also all a full correlation matrix, but I
haven't had a need for that yet.

On Sun, Feb 22, 2009 at 11:24 AM, Dimitri Pourbaix <
> wrote:

> Either one considers the full weighting matrix (including potential
> correlation between observations) or one does not account for any weight
> at all.  By premultiplying both the function matrix and the observation
> vector  by the square root of the weight matrix, one can forget about it
> completely in the rest of the computation.

Ted Dunning, CTO

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