Use aggregate:
aggregate(x['Value'], x[c('Factor1', 'Factor2')], mean)
On Mon, Dec 7, 2009 at 8:25 AM, Ivan Calandra
<ivan.calan...@uni-hamburg.de> wrote:
> Hi everybody,
>
> I would like to compute the mean for 1 variable between the rows with the
> same levels.
>
> For example, with the dataset below:
> Factor1 Factor2 Value
> A X 1
> A X 2
> A Y 3
> A Y 4
> B X 5
> B X 6
> B Y 7
> B Y 8
>
> I would like to get:
> Factor1 Factor2 Value
> A X 1.5
> A Y 3.5
> B X 5.5
> B Y 7.5
>
> Up to now, I worked in Statistica and Systat, and it was called "column
> statistics" in Statistica (and I had a script with the "BY" function in
> Systat).
>
> Of course it is a simplified case. For my dataset I have 4 factors and 15
> variables, so a general method would be nice. However, my skills are not
> that great, so if you could please give some explanations (I mean other than
> what is in the ?function of course).
>
> Thanks a lot in advance
> Ivan
>
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>
--
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O
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