[R] Odp: sampling problem - new to R

From: Petr PIKAL <petr.pikal_at_precheza.cz>
Date: Wed, 06 Jun 2007 15:57:05 +0200


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:
http://www.nabble.com/sampling-problem---new-to-
> R-tf3872130.html#a10970708
> Sent from the R help mailing list archive at Nabble.com.
>
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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. Received on Wed 06 Jun 2007 - 14:10:37 GMT

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