Andreas,
Thanks alot. I combined below and other suggestions given on r-help and it
worked.
--- On Fri, 4/8/11, Andreas Borg <andreas.b...@unimedizin-mainz.de> wrote:
From: Andreas Borg <andreas.b...@unimedizin-mainz.de>
Subject: Re: [R] random sampling with levels and with replacement
To: tab...@yahoo.com
Cc: "R help" <r-help@r-project.org>
Date: Friday, April 8, 2011, 11:13 AM
Hi,
I am not perfectly sure what you want to do, but here is what I would do
to maintain good/bad ratio in the sample (as Daniel posted, split the
data and sample from the groups):
df <- data.frame(V1 = 1:400, V2 = c(rep("good",360), rep("bad",40)))
isGood <- which(df$V2=="good")
isBad <- which(df$V2=="bad")
sampleGood <- df[sample(isGood, replace=TRUE),]
sampleBad <- df[sample(isBad, replace=TRUE),]
summary(rbind(sampleGood, sampleBad))
Please include a more specific example with test data (for "final" in
this case) next time.
Best regards,
Andreas
taby gathoni schrieb:
> Dear all,
> i have a dataset of about 400 records , with a variable that has two levels
> 40 bad and 360 good among other variables,how do i come up with10 random
> samples that have the composition of as the main sample but maintaining the
> 40 bad 360 good with replacement, i recently discovered that my random
> samples generated dont maintain the ratio. My code is as :
>
> mysample <- final[sample(1:nrow(final), 400,replace=TRUE),]
>
> does not give me the ratio of 40 bad and 360 good can anyone give me some
> pointers please?
>
>
>
> Thanks,
> Taby
>
>
>
>
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>
>
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--
Andreas Borg
Medizinische Informatik
UNIVERSITÄTSMEDIZIN
der Johannes Gutenberg-Universität
Institut für Medizinische Biometrie, Epidemiologie und Informatik
Obere Zahlbacher Straße 69, 55131 Mainz
www.imbei.uni-mainz.de
Telefon +49 (0) 6131 175062
E-Mail: b...@imbei.uni-mainz.de
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