[R] glm

Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Mon Nov 6 00:51:26 CET 2000

"Antonio Olinto" <aolinto at bignet.com.br> writes:

> Hi to all,
> So I'm also a new user. I downloaded the program last week and I think =
> it's great. Thanks to those who have developed R.
> I have a special interest in GLM as a tool to describe fisheries and its =
> variables and I'm just begging to study it.

First: glm in R is not PROC GLM in SAS. In R the "G" is for
"generalized", cf. GLIM or GENMOD in SAS. The SAS GLM (General Linear
Model) functionality comes via lm() and friends in R.

> As I could understand there's two types of GLM sun of squares: in "type =
> I" the factors are added in sequence and "type III" this sequence =
> doesn't matter. In R I always get the message: "Terms added sequentially =
> (first to last)".

I wouldn't say it "doesn't matter". Rather, it is "testing with
replacement" - see if you can drop a term, then put it back in the
model and see if you can drop another term.

> Is there any way to make the so called Type III procedure?

Essentially, drop1() - barring details concerning main effects with 
interaction terms present.

   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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