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sum2
2005 Apr 15
4
aggregation question
Is length(unique()) what you are looking for?
Andy
> From: Christoph Lehmann
>
> Hi I have a question concerning aggregation
>
> (simple demo code S. below)
>
> I have the data.frame
>
> id meas date
> 1 a 0.637513747 1
> 2 a 0.187710063 2
> 3 a 0.247098459 2
> 4 a 0.306447690 3
> 5 b 0.407573577 2
> 6 b