Re: [R] Problem with multinom ?

From: Marc Girondot <marc.girondot_at_ese.u-psud.fr>
Date: Sun 12 Jun 2005 - 05:15:50 EST

>Dear Marc,
>
>I get the same results -- same coefficients, standard errors, and fitted
>probabilities -- from multinom() and glm(). It's true that the deviances
>differ, but they, I believe, are defined only up to an additive constant:
>
>> predict(dt.b, type="response")
> 1 2 3
>0.4524946 0.5032227 0.5538845
>
>> predict(dt.m, type="probs")
> 1 2 3 4 5 6
>0.4524948 0.4524948 0.5032229 0.5032229 0.5538846 0.5538846
>
>These fitted probabilities *are* correct: Since the members of each pair
>(1,2), (3,4), and (5,6) have identical values of factor they are identical
>fitted probabilities.

I expected rather to obtain (note 1- before some terms):
> 1 2 3 4 5 6
0.4524948 1-0.4524948 0.5032229 1-0.5032229 0.5538846 1-0.5538846

...

Marc

-- 

__________________________________________________________
Marc Girondot, Pr
Laboratoire Ecologie, Systématique et Evolution
Equipe de Conservation des Populations et des Communautés
CNRS, ENGREF et Université Paris-Sud 11 , UMR 8079
Bâtiment 362
91405 Orsay Cedex, France

Tel:  33 1 (0)1.69.15.72.30   Fax: 33 1 (0)1 69 
15 56 96   e-mail: marc.girondot@ese.u-psud.fr
Web: http://www.ese.u-psud.fr/epc/conservation/Marc.html
Skype: girondot
Fax in US: 1-425-732-6934

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Received on Sun Jun 12 05:21:53 2005

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