On Thu, 4 Sep 2008, ONKELINX, Thierry wrote:
Dear Luc,
You should send this kind of questions to the general mailing list
([EMAIL PROTECTED]) instead of the developer list.
To answer your question: have a look at ?by and ?aggregate
And ?ave .
HTH,
Thierry
-----Oorspronkelijk bericht-----
Van: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Namens RFTW
Verzonden: donderdag 4 september 2008 9:07
Aan: r-devel@r-project.org
Onderwerp: [Rd] calculating means per group
Hi all
I have a very basic question, yet i have not found how to do it.
Suppose my dataset looks like this:
Year Area value
1 a 20
1 a 25
1 a 28
1 a 31
1 a 23
1 b 25
1 b 28
1 b 23
1 b 19
2 a 25
2 a 23
2 a 24
2 a 26
2 b 27
2 b 28
2 b 20
2 b 25
2 b 28
Now, i want to calculate a MEAN per year per area. How do i do that?
With mean(value) i calculate the mean of all values of course. I just
need
to know how to group year and area correctly.
I assume that i can use this grouping in other calculations too, right?
Cheers,
Luc
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Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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