That is just what I wanted :-) 
For me it is incredible... all in one single line.
Thank you!

Federico


Philipp Pagel wrote:
>> I would like to obtain a data.frame or matrix in which rows with an
>> equal string on column "C1" are averaged. In the previous example, rows
>> "One", "Four" and "Five" should be averaged because the three have "A"
>> con C1. The resulting row should be: "A"  10/3  28/3   46/3
>>     
>
> I think this is waht you are looking for:
>
> aggregate(df[-1], by=list(C1=df$C1), mean)
>
> cu
> 	Philipp
>
>   


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