This should create your samples:

x <- "Tree      Plot
56749    1
63494    1
87375    1
37494    2
92753    3
34847    3
38747    4 "
x <- read.table(textConnection(x), header=TRUE)
for(i in 1:10){  # take 10 sample
    # partition data by plot
    z <- by(x, x$Plot, function(.plot){
        .plot[sample(nrow(.plot),1),]  # choose a random sample from the
plot
    })
    z <- do.call('rbind', z)  # create dataframe
    print(z)
}




On 6/5/07, baldeck <cabaldeck@yahoo.com> wrote:
>
>
> I have a data set of individual trees and the plots that they are in:
>
> Tree      Plot
> 56749    1
> 63494    1
> 87375    1
> 37494    2
> 92753    3
> 34847    3
> 38747    4 etc...
>
> So each plot is represented once for every individual that occurrs in it.
> Plots get different numbers of rows because there can be a different
> number
> of individuals in each plot.
>
> I want to make a data frame that consists of one individual from each
> plot.
> I would like to randomly choose one individual from each plot that is
> present in the data set.  I will have to do this to multiple data sets
> which
> may contain different plots, and may contain up to 1200 plots, so I can't
> choose the plots by hand.
>
> Please help me with this.  I'm an ecologist and I'm in Panama, with no one
> around who is educated in R.  Whoever solves this problem for me will be
> acknowledged in any resulting publications.
>
> Thanks!
> -Claire
> --
> View this message in context:
> http://www.nabble.com/sampling-problem---new-to-R-tf3872130.html#a10970708
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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