On Fri, 29 Oct 2004, CG Pettersson wrote:
> I have been using R for two years, but still have trivial problems.
> For the moment, I run R1.9.1 on a W2k computer.
Time to read a book! This sort of thing is discussed at length in Chapter
2 of MASS4 (see the FAQ), for example. It even discusses why your example
does not work.
> I work with a dataset from a variety evaluation project. Every year 25
> varieties have been tested. The tested cultivars have been the same
> each year in all trials, but some have changed over the three year
> period. Now I want to do some calculations and plotting on subsets.
> The structure looks like this:
>
> Year ADB Block Vcode Variety Yield Protein
> 2002 SW0024 1 20226 Denise 5843 12.8....
> 2002 SW0024 1 9865 Astoria 6729 11.4
> 2002 SW0024 1 9622 Barke 6121 12
> 2002 SW0024 1 9604 Cecilia 5579 12.7
> 2002 SW0024 1 20223 Granta 5591 11.6
> 2002 SW0024 1 20222 Class 5591 11.7
> 2002 SW0024 1 9922 Wiking 5744 12.5
> 2002 SW0024 1 20103 Vortex 5863 10.6
> .
> .
> And so on both down and sideways.
> Three years and four trials with three replicats each gives 900 lines.
>
> How do I use several criteria to subset this?
>
> Ast <- subset(data, Variety == "Astoria")
>
> works fine giving back the 36 lines where Astoria appears.
> But how do I pick two (or more) varieties? AND picking one (or two)
> years?
>
> Everything I have tried results in rubbish, like:
>
> AstBark <- subset(data, Variety == c("Astoria","Barke"))
Variety %in% c("Astoria","Barke") is probably what you intended.
You can pick also on years by using & in the indexing criterion.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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