Re: proportionality constraints (fwd)

Dear Ian,

Indeed your email was distributed but apparantly nobody has or is willing
to offer a solution.

The relationship matrix stuff in Genstat is, as far as I know, the same as
is available
in ASReml. I do not think it helps with your situation.

While the concept of enabling what you want has been around for years, a
suitable
syntax and procedure has not been implemented.

The best I could offer, using the beta version, is to extract the
information matrix and score
from the unconstrained model after an iteration and derive new constrained
parameters from that.
Refit the model with the updated parameters and iterate the process to
convergence.

The relevant qualifier is !SCORE.

Another idea is
 In ASReml, I have to let v2=k*v1,
v3=(1+0.5*k)*v1, and then calculate a profile likelihood for a range of
values of k.

The !VCC qualifier allows you to fix the relationship between v2 and v1 by
nominating k
So, for a given k, estimate v1 and v3 (with v2=k*v1).

Given v1 and v3 estimated, solve k=2(v3/v1 -1)

and repeat the process until convergence.

I apologise for not responding earlier.

with God's love in the Name of Jesus Christ.
Check out http://members.dodo.net.au/~cargovale

Arthur Gilmour PhD
Principal Research Scientist (Biometrics)
NSW Department of Primary Industries
Orange Agricultural Institute, Forest Rd, ORANGE, 2800, AUSTRALIA

mailto:Arthur.Gilmour_at_agric.nsw.gov.au
fax: 02 6391 3899; 02 6391 3922 Australia +61
telephone work: 02 6391 3815; home: 02 6364 3288;

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Date: Thu, 21 Apr 2005 13:00:38 +0100 (BST)
From: I M S White <iwhite_at_staffmail.ed.ac.uk>
To: asreml-l_at_agric.nsw.gov.au
Cc: Robin Thompson <robin.thompson_at_bbsrc.ac.uk>
Subject: proportionality constraints

If there are (say) three variance components, v1, v2, and v3, I think
Genstat REML allows me to set a constraint such as v3 = v1 + 0.5 * v2
(using VCOMP[RELATIONSHIP=matrix]). In ASReml, I have to let v2=k*v1,
v3=(1+0.5*k)*v1, and then calculate a profile likelihood for a range of
values of k.

(1) Is there a better way? (2) Is there any reason why ASReml cannot
provide the more general form of constraint?

======================================
I.White
University of Edinburgh
Ashworth Laboratories, West Mains Road
Edinburgh EH9 3JT
Tel: 0131 650 5490 Fax: 0131 650 6564
E-mail: iwhite_at_staffmail.ed.ac.uk
======================================

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Received on Tue May 04 2005 - 13:05:38 EST