On 25 Oct 2005 at 13:48, Stephen Choularton wrote:
From: "Stephen Choularton" <mail at bymouth.com>
To: "R Help" <r-help at stat.math.ethz.ch>
Date sent: Tue, 25 Oct 2005 13:48:42 +1000
Subject: [R] selecting every nth item in the data
> I want to make a glm and then use predict. I have a fairly small
> sample (4000 cases) and I want to train on 90% and test on 10% but I
> want to do it in slices so I test on every 10th case and train on the
> others. Is there some simple way to get these elements?
As glm accept subet you probably can use
test<-seq(1,4000,n)
glm(...., subset = test)
to select only n'th item or
glm(...., subset = -test)
to select all but n'th items.
or you can split the data freme by
mydf[test,] or mydf[-test,]
HTH
Petr
>
> Stephen
>
> --
>
>
>
> 21/10/2005
>
>
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Petr Pikal
petr.pikal at precheza.cz