R help - Jun 2012 - Problem with sample function

Dear list
Is there a way  to extract a random sample without duplicated row from a
dataframe ?.
a=c(1,2,3,1,1,1,2,1)
 b=c(1,2,3,1,2,1,2,1)
 c=c(1,1,1,1,1,1,1,1)
 d=c(1,2,3,1,1,1,2,1)
 prov<-data.frame(a,b,c,d)
prov2<-prov[sample(1:nrow(prov),5,replace=T),]
prov2
    a b c d
3   3 3 1 3
6   1 1 1 1
3.1 3 3 1 3
5   1 2 1 1
8   1 1 1 1

I tryed  the above code but as you can see sample function includes also
duplicates.
thank you for any tip
Guido

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Dear Guido,

Try

prov2<-prov[sample(1:nrow(prov),5,replace=F),] 

which corresponds to without replacement sampling.

Best
Ozgur

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On Jun 8, 2012, at 12:33 PM, Guido Leoni wrote:
> Dear list
> Is there a way  to extract a random sample without duplicated row  
> from a
> dataframe ?.
> a=c(1,2,3,1,1,1,2,1)
> b=c(1,2,3,1,2,1,2,1)
> c=c(1,1,1,1,1,1,1,1)
> d=c(1,2,3,1,1,1,2,1)
> prov<-data.frame(a,b,c,d)
> prov2<-prov[sample(1:nrow(prov),5,replace=T),]
> prov2
>    a b c d
> 3   3 3 1 3
> 6   1 1 1 1
> 3.1 3 3 1 3
> 5   1 2 1 1
> 8   1 1 1 1
>
> I tryed  the above code but as you can see sample function includes  
> also
> duplicates.
> thank you for any tip
Why would you use replace=T if you didn't want duplicates???

-- 

David Winsemius, MD
West Hartford, CT