Re: [R] Anova of a nls object

From: <Bill.Venables_at_csiro.au>
Date: Thu, 20 Mar 2008 08:17:20 +1000

You don't, because the operation is not well defined.

Using anova( ) on a single linear model object will fit a sequential sequence of sub-models got by adding the terms into the linear model, as they appear in the model formula, one by one.

In non-linear regression there is no unique definition of sub-model. You may have a non-linear regression consisting of a sum of terms, but if that's the way you wish to define the sequential decomposition, you have to do so explicitly and fit the models by hand.

(Some people have doubts about the wisdom of allowing anova() even on a single linear model object, since the sequential of sub-models used is arbitrary even there. I think this view has a lot going for it.)

Bill Venables
CSIRO Laboratories
PO Box 120, Cleveland, 4163
AUSTRALIA

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-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of Eric Ferreira
Sent: Thursday, 20 March 2008 4:21 AM
To: r-help_at_r-project.org
Subject: [R] Anova of a nls object

Dear useRs,

How can I perform the analysis of variance of just one nls object?

Regards

-- 
Eric B Ferreira
Exact Sciences Department
Federal University of Lavras
Minas Gerais - Brazil

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Received on Wed 19 Mar 2008 - 22:23:13 GMT

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