[R] Help with "by"

[David Winsemius]

On Apr 4, 2009, at 3:42 PM, AllenL wrote:

>
> Searched for "by" in forums and no hits, should be simple problem.

The help page for by must surely have have *some* information?

>
>
> 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?

A) You are not providing an example that can be worked on.
B) You are not providing the output of your session.
C) You are not describing Data, Plot and AbvBioAnnProd.

Wild assed guess:
bio.mean <- by(Data$AbvBioAnnProd, Data$Plot, mean )

>

David Winsemius, MD
Heritage Laboratories
West Hartford, CT