[R] Select values at random by id value

[hadley wickham]

On Thu, Jul 2, 2009 at 8:15 AM, James Martin<just.struttin at gmail.com> wrote:
> Hadley, Sunil, and list,
>
> This is not quite doing what I wanted it to do (as far as I can tell). I
> perhaps did not explain it thoroughly.  It seems to be sampling one value
> for each day leaving ~200 observations. I need for it randomly chose one hab
> value for each bird if there is more than one value for a given day, I will
> try and example below.
>
> id,date,location2,hab
>
> 1,05/23/06,0,1
> 1,05/23/06,0,2
> 1,05/23/06,0,1
>
> So in this case the animal was located 3 times on may 23rd but I only want
> one of the locations and instead of arbitrarily choosing one I wanted to
> randomly sample one.

ddply(df, c("date", "location"), function(df) df[sample(nrow(df), 1), ])

Hadley

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