[R] determine dimension on which by() applies

[Gabor Grothendieck]

By works on the rows or first dimension.  See ?by, ?apply, ?aperm
?tapply

On 4/5/06, Werner Wernersen <pensterfuzzer at yahoo.de> wrote:
> Hi,
>
> having solved one problem with your kindest help I
> directly ran into the next one:
> I now have a 4-dimensional array and I want to
> aggregate subsets (sum up over) for some of the
> dimensions. This sort of aggregating works beautifully
> for matrices with by(). Is there a similar function
> where I additionally can choose the dimension to do
> the group calculations over?
>
> Thanks again!
>  Werner
>
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