[R] Odp: sampling problem - new to R

[Petr PIKAL]

Hi

If I understand correctly, use split and sample with lapply. If DF is your 
dataframe

lapply(split(DF$Tree, DF$Plot), function(x) sample(x,1))

shall select random tree from each plot. Or you can get it in tabular form 
with sapply.

Regards
Petr

r-help-bounces at stat.math.ethz.ch napsal dne 05.06.2007 16:29:49:

> 
> 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: 
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> R-tf3872130.html#a10970708
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