(apologies for any double hits; forgot to reply all...)

Or, you could just go back to basics, and write yourself a general loop that
goes through whatever levels of a variable and gives you back whatever
statistics you want... below is an example where you estimate means for each
level, but you could estimate any number of statistical parameters...

dat<-data.frame(c(rep("A",5), rep("B",5),rep("C",5)),c(1:15))
results<-NULL
for(i in levels(dat[,1]))
      {
      sub.dat<-subset(dat, dat[,1]==i)
      res<-mean(sub.dat[,2])
      results<-c(results,i,res)
      }
results.mat<-matrix(results, ncol=2, byrow=TRUE)
results.mat


HTH,

Mike

On Thu, Nov 4, 2010 at 7:28 AM, Ramsvatn Silje <silje.ramsvatn@uit.no>wrote:

>
> Hello,
>
> I have tried to find this out some other way, but unsuccessful I have to
> try this list.
> I assume this should be quite simple.
>
> I have a dataset with 4 columns, "Sample_no", "Species", "Nitrogen",
> "Carbon" in csv format. In the species column I have many different
> species with varying number of obs per species
>
> Eg
>
> "Sample_no"     "Species"       "Nitrogen"      "Carbon"
> 1               Cod             15.2            -19.0
> 2               Haddock 14.8            -20.2
> 3               Cod             15.6            -18.5
> 4               Cod             13.2            -20.1
> 5               Haddock 14.3            -18.8
> Etc..
>
> And I want to calculate, mean, standard dev etc per species for the
> observations "Nitrogen" and "Carbon". And later do plots and stats with
> the different species. I will in the end have many species, so need it to
> be "automatic" I can't enter code for every species separate.
>
> Can anyone help me with this? Or if this is the wrong list to sendt this
> question to, where do I send it?
>
> Thank you very much in advance.
>
>
> Best regards
>
> Silje Ramsvatn
>
> PhD-candidate
> University of Tromsų
> Norway
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>

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