[R] Forcing model parameters to a constant (in GLMs)

From: David Reitter <david.reitter_at_gmail.com>
Date: Wed 14 Dec 2005 - 03:00:41 EST


Hi,

I'm looking for a way to bind specific model parameters to a constant
(in my case: 0) before fitting the model. I'm fitting multinomial
logistic regression models (via glm()).
Assuming a model with a categorial response variable c {c1,c2,c3} that is a matrix like

c2: b2 b2.1 b2.2 b2.3
c3: b3 b3.1 b3.2 b3.3,

I would like to force, e.g. b2.1, b3.1 and b2.3 to 0 before estimating the other parameters.

I'm aware of a similar - unresolved - question on list list back in July:

https://stat.ethz.ch/pipermail/r-help/2005-July/075042.html

The "offset" in an interaction term doesn't seem to do what I want - as far as I can see, it manipulates the intercept, and it's additive
(i.e. an intercept is estimated anyways).

Thanks
David

--
David Reitter - ICCS/HCRC, Informatics, University of Edinburgh

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Received on Wed Dec 14 03:40:36 2005

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