> -----Original Message-----
> From: Prof Brian Ripley
> Sent: Monday, August 23, 2004 1:15 PM
> To: Trenkler, Dietrich
> Subject: Re: [R] Two factor ANOVA with lm()
>
> On Mon, 23 Aug 2004, Trenkler, Dietrich wrote:
>
> [...]
>
> > outset? Or put another way: Why is it that lm() uses the corner point
> > constraints by default? Where can I find a documentation for this
> > behavior?
>
> In almost any piece of documentation on linear models in R, including the
> FAQ and `An Introduction to R', which says
>
> The main reason for mentioning this is that R and S have different
> defaults for unordered factors, S using Helmert contrasts. So if you
> need to compare your results to those of a textbook or paper which used
> S-PLUS, you will need to set
>
> options(contrasts = c("contr.helmert", "contr.poly"))
>
> This is a deliberate difference, as treatment contrasts (R's default)
> are thought easier for newcomers to interpret.
>
> Now, what does the posting guide say about doing your homework?
[Dietrich Trenkler] I swear I didn't need it for a homework.
I just overlooked the self-evident... (blush)
Thank you.
D. Trenkler
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