[R] sampling problem - new to R

[Doran, Harold]

I dealt with something like this recently. 

x <- data.frame(plot = gl(2,5), tree = rnorm(10)) 
y <- split(x, x$plot)

ss <- numeric(2)
for(i in 1:2){
	ss[i] <- sample(row.names(y[[i]][1]), 1)
}

z <- x[ss,]

People help out of the goodness of the hearts and not for publication
recognition. 

Harold


> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of baldeck
> Sent: Tuesday, June 05, 2007 10:30 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] sampling problem - new to R
> 
> 
> 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.ht
> ml#a10970708
> Sent from the R help mailing list archive at Nabble.com.
> 
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