[R] Generalized linear model

Marcos Sanches marcos_sanches at gallup.com
Mon Nov 17 16:24:03 CET 2003

	Ok, it worked!!!

  But what would be the command if I want to eliminate another point? I
mean, two points at the same time.



-----Original Message-----
From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk]
Sent: Monday, November 17, 2003 1:02 PM
To: Marcos Sanches
Cc: R-Help
Subject: Re: [R] Generalized linear model

The second fit appeared to use a dataframe and the first did not.  Try

fit2<-glm(canc~id1+year1+time+lnpa,family=poisson, subset=-18)

On Mon, 17 Nov 2003, Marcos Sanches wrote:

> 	Hi all!
>  I am fitting a Poisson model, using the following command:
> > fit2<-glm(canc~id1+year1+time+lnpa,family=poisson)
>  where 'id1', 'year1' and 'time' are factors. I defined them with:
> > id1<-C(factor(id1), treatment)
>  and 'lnpa' is a continuous variable.
> The 'summary' function gives me all the effects estimates, that is, for
> I end up with estimates for id12, id13 and id14, the id11 is the reference
> level. That is fine, but when I try to fit the model without the point 18,
> using the command line:
> > fit2<-glm(canc~id1+year1+time+lnpa,family=poisson, subset(dat,
> The 'summary' function stop to giving me the levels effect, and gives only
> one effect for id1, one for year1, one for time and one for lnpa. I want
> have the parameters estimates for each level of each factor, as it was in
> the first fit. Also, I noticed the degree of freedom of deviance and the
> deviance itself has increased, so I cont't compare both models in terms of
> their deviance.
>  What should I do to have each factor level effect as I had in the first
> case?
>  Thanks
> Marcos
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Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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