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[S] Two questions concerning GAM

To: s-news@wubios.wustl.edu
Subject: [S] Two questions concerning GAM
From: "Claudio Conversano" <CONVERSAN@dms.unina.it>
Date: Mon, 25 Jan 1999 12:53:48 +1
Organization: dmsna
Sender: owner-s-news@wubios.wustl.edu
Dear S+ users:

I'am using for the first time S-Plus 4.0 under Win95, and I'am working with 
Generalized 
Additive Models.
After having estimated the model using the function gam, I can get an 
anova-like table showing me, as is reported in the on-line manual, 
 the non-linear effect of each predictor included in the model.
I have to explain the effect of about 30 predictors over my response 
variable, and when I increase the number of predictor entered I note 
that some of them entered before are not significant anymore 
(i.e. they have associated an high F or Chisq value).

My first question is:
Is there any criterion to set the order of the predictor to be 
included in the model?

Furthermore, I used the following expression of the function predict.gam 
in order to predict my new values of the dependent variable, supplying 
a "newdata"  object.

mib1.gam.pred.new<-
predict.gam(mib1.gam,mibp1gam,type="response")


I get the following error message: 
Error in .Fortran("lowese",: extrapolation not allowed with blending
Dumped
Warning messages:
1: eval MbPjt? -0.085908
 in: .Fortran("lowese",  ...
2: lowerlimit eval MbPjt? -0.07646
 in: .Fortran("lowese",  ...

Could anyone explain me what does it mean?

Thanks in advance.
Claudio
       ,,,
      (o o)                                            
--oOO--(_)--OOo-------------------------------------------------------
                         Claudio Conversano
                            Ph.D. Student
             Dipartimento di Matematica e Statistica
                     Via Cintia Monte S. Angelo
                           I-80126 NAPOLI
                               ITALY
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