From p.dalgaard@biostat.ku.dk  Tue Jan  6 12:21:52 1998
From: p.dalgaard@biostat.ku.dk (Peter Dalgaard BSA)
Date: 06 Jan 1998 13:21:52 +0100
Subject: R-beta: More glm bugs
In-Reply-To: Martin Maechler's message of Tue, 6 Jan 1998 11:36:18 +0100
References: <199801061036.LAA02319@sophie.ethz.ch>
Message-ID: <x21zylkd27.fsf@blueberry.kubism.ku.dk>

Martin Maechler <maechler@stat.math.ethz.ch> writes:

> The following, I think is more a problem  of  model.matrix(.) and such lower
> level functions which I leave for  Thomas and Ross ...
> 
>     Jim> 3. The following two lines should produce the same result but don't:
>     Jim> glm(y~x1:x2:x3-x1:x2:(1+x3))
>     Jim> glm(y~x1:x2:x3-x1:x2:-x1:x2:x3)
>     Jim> Only the second gives the correct answer. I have not tried to fix this.

There seems to be a typo in Jims 2nd example (extra :) (no, that was
not a smiley...). However, the problem seems to boil down to this:

> model.matrix(~x1:x2:1)
     (Intercept)
[1,]           1
[2,]           1
[3,]           1
[4,]           1
[5,]           1
[6,]           1
[7,]           1
[8,]           1
attr(,"assign")
[1] 0

Which is pretty clearly wrong. It should be the same as ~x1:x2

-- 
   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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R-beta: More glm bugs
Peter Dalgaard BSA