Try this:
score[tapply(rownames(score), score$id, tail, 1),]
On 6/12/06, Tony Chu <[EMAIL PROTECTED]> wrote:
> Dear R users:
>
> I have a small test dataframe as the follows :
>
> math = c(80,75,70,65,65,70)
> reading = c(65,70,88,NA,90,NA)
> id = c('001','001','001','002','003','003')
> score = data.frame(id, reading, math)
>
> > score
> id reading math
> 1 001 65 80
> 2 001 70 75
> 3 001 88 70
> 4 002 NA 65
> 5 003 90 65
> 6 003 NA 70
>
> Could someone advise me tips about how to select the last row from
> each id group of 001, 002, & 003?
>
> In other words, the rows I need are :
>
> id reading math
> 3 001 88 70
> 4 002 NA 65
> 6 003 NA 70
>
> I tried function sebset but could not go very far. Thanks !
>
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