From: Faheem Mitha <faheem@email.unc.edu>
To: Mikael Adlers <mikael@mathcore.com>
Cc: <gsl-discuss@sources.redhat.com>
Subject: RE: (HH^t)^{-1}
Date: Wed, 19 Dec 2001 13:20:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.33.0110111149390.24042-100000@Chrestomanci> (raw)
In-Reply-To: <4DFD94A38EB3104E838576A77AEBB36E166DAC@hermes.mathcore.se>
On Thu, 11 Oct 2001, Mikael Adlers wrote:
> The problem of computing \mu is a least squares problem. What you
> have written is the normal equations to
>
> min || H\mu - h||_2
>
> Another way is to solve the problem by QR factorization, H = Q*R,
> ||H\mu -h||_2 = ||R \mu - Q^Th||_2. To solve this you solve R \mu = Q^Tb
> This method has much better error bounds and should be preferred.
Dear Mikael Adlers,
Thanks, this is a really good suggestion. I was handed these expressions
by someone else (I think they come from Bayesian computations) but I
haven't checked them myself. Like a ninny, I didn't realise /mu was a
solution to a least squares problem. This way of handling it is certainly
much better than the clumsy things I was doing. Thanks a lot for pointing
it out.
Sincerely, Faheem Mitha.
next prev parent reply other threads:[~2001-12-19 13:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-19 13:20 (HH^t)^{-1} Mikael Adlers
2001-12-19 13:20 ` Faheem Mitha [this message]
[not found] <20011010212301.23259.qmail@web20705.mail.yahoo.com>
2001-12-19 13:20 ` (HH^t)^{-1} Faheem Mitha
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