[R] Help with "by"

Uwe Ligges ligges at statistik.tu-dortmund.de
Sat Apr 4 23:36:08 CEST 2009

AllenL wrote:
> Searched for "by" in forums and no hits, should be simple problem.
> This is my line:
>> bio.mean<-by(Data,Plot, function(x) mean(AbvBioAnnProd))
> I want to calculate the mean of "AbvBioAnnProd" in each Plot. What am I
> doing wrong?

What is AbvBioAnnProd? I only see that you pass Data, Plot and the parts 
  of Data subscripted by Plot as x into the anonymous function, but 
there is no AbvBioAnnProd that mean can use so far ...
You need to tell us why R should know anything about that object.

Uwe Ligges

> Thanks in advance,
> -AL

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