[R] aov and non-categorical variables

[kjetil@entelnet.bo]

On 15 Oct 2003 at 9:32, Alexander Sirotkin [at Yahoo] wrote:

> It is unclear to me how aov() handles non-categorical
> variables.

aov is an interface to lm, so it can estimate every model lm
can, the difference is that it produces the results (summary)
in the classical way for anova.

> 
> I mean it works and produces results that I would
> expect, but I was under impression that ANOVA is only
> defined for categorical variables.
> 
> In addition, help(aov) says that it "call to 'lm' for
> each  stratum", which  I presume means that it calls
> to lm() for every group of the categorical variable, 

No. With anova you can also define "error strata" using 
Error() as part of the formula, lm() cannot do that. If you don't use 
Error() in the formula, lm() is called only once. 

Kjetil Halvorsen

> however I don't quite understand what this means for
> non-categorical variable.
> 
> Thanks
> 
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