I would use duplicated. I would first merge the data.frames and then see
which are duplicated like so:

> bigger <- rbind(mydata, myExtract.data)
> bigger[duplicated(bigger), ]
  ID V  B
7  4 4 40
8  5 4 40

This may not be viable if you're working with data that won't fit into your
RAM (after the merge).


Cheers,
Roman



On Thu, Sep 15, 2011 at 3:02 PM, gianni lavaredo
<gianni.lavaredo@gmail.com>wrote:

> Dear Reserchers,
>
> sorry if I post here this help request but it's part of Remote Sensing
> Analysis. I have a huge df where I need to select and extarct the row with
> the same value. Following a small example:
>
>
> mydata <-
> data.frame(ID=c(1,2,3,4,5,6),V=c(1,2,3,4,4,6),B=c(10,20,30,40,40,60))
>
>  ID V  B
> 1  1 1 10
> 2  2 2 20
> 3  3 3 30
> 4  4 4 40
> 5  5 4 40
> 6  6 6 60
>
>
> myExtract.data
> ID V B
> 4  4 40
> 5  4 40
>
>
> because in V and B there are the same value
>
> thanks in advance
>
> Gianni
>
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>
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-- 
In God we trust, all others bring data.

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