[R] Removing rows in dataframe w'o duplicated values

[David Winsemius]

On Nov 22, 2011, at 12:43 PM, AC Del Re wrote:

> Hi,
>
> Is there an easy way to remove dataframe rows without duplicated  
> values of
> a specified column ('id')?  e.g.,
>
> dat <- data.frame(id = c(1,1,1,2,3,3), value = c(5,6,7,4,5,4),  
> value2 =
> c(1,4,3,3,4,3))
> dat
>
>  id value value2
> 1  1     5      1
> 2  1     6      4
> 3  1     7      3
> 4  2     4      3
> 5  3     5      4
> 6  3     4      3

 > dat[ave(dat$id, dat$id, FUN=length) >1, ]
   id value value2
1  1     5      1
2  1     6      4
3  1     7      3
5  3     5      4
6  3     4      3


>
>
> This is sample data and the real data has hundreds of rows. In this
> case, only row 4 does not have a duplicated id and I would like to
> remove it without using:
>
>
> dat$id[4] <- NULL
>
>
> Any help is appreciated!
>
>
> AC
>
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>
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David Winsemius, MD
West Hartford, CT