Re: R-beta: Various R Questions and Comments

Peter Dalgaard BSA (p.dalgaard@biostat.ku.dk)
16 Feb 1998 20:33:31 +0100


To: morse@pobox.com (Doug Morse)
Subject: Re: R-beta: Various R Questions and Comments
From: Peter Dalgaard BSA <p.dalgaard@biostat.ku.dk>
Date: 16 Feb 1998 20:33:31 +0100
In-Reply-To: morse@pobox.com's message of Mon, 16 Feb 1998 13:12:06 -0600 (CST)

morse@pobox.com (Doug Morse) writes:

> > >     
> > >        Res.Df  Res.Sum-Sq  Df  Sum-Sq       F  Pr(>F)
> > >     1      21        2152
> > >     2      19        2012   2   139.9  0.6609  0.5279
> > >     -----
> > >     
> > >     It represents a test of whether beta1 = -1.0 and beta2 = 0.0
> > >     using the generalized linear test statistic (see "Applied
> > 
> > Wouldn't this be better done using offsets?
> 
> I'm not sure what you mean by 'offsets'.  Could you elaborate a
> bit?

Whoops, sorry. That feature is glm only (I wonder why...). Basically:


glm(formula = Ozone ~ Day)

..
Coefficients:
               Value  Std.error  t value  P(>|t|)
(Intercept)  42.9039     6.2883   6.8228   0.0000
Day          -0.0499     0.3531  -0.1412   0.8879

glm(formula = Ozone ~ Day + offset(-Day/20))

..
Coefficients:
               Value  Std.error  t value  P(>|t|)
(Intercept)  42.9039     6.2883   6.8228   0.0000
Day           0.0001     0.3531   0.0004   0.9997


(lm() just silently disregards the offset term. Needs fixing, obviously...)
-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907

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