Re: [R] Generalized linear model

[Spencer Graves]

     From "?glm", I find the following: 

    subset: an optional vector specifying a subset of observations to be
             used in the fitting process.
     Thus, to delete observations 16 and 18, I can use the following: 

fit2<-glm(canc~id1+year1+time+lnpa,family=poisson, subset=-c(16,18))

hope this helps.  spencer graves

Marcos Sanches wrote:

	Ok, it worked!!!

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

Marcos

-----Original Message-----
From: Prof Brian Ripley [mailto:[EMAIL PROTECTED]
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
   

id1,
 

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,
     

order!=18))
 

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
   

to
 

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,                  [EMAIL PROTECTED]
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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