[R] data frame select max group by like function

[Henrique Dallazuanna]

Try this:

library(sqldf)
sqldf("SELECT ID, Year, MAX(score) FROM DF GROUP BY ID")

Or

do.call(rbind, lapply(split(DF <- DF[order(DF$score),], DF$ID), tail, 1))

On Tue, Mar 9, 2010 at 3:35 PM, Tan, Richard <RTan at panagora.com> wrote:
> Hi, I have a data frame with 3 columns: ID, year and score.  How can I
> select for each unique ID, the year that has the max score?  For
> example, for data frame
>
> ID, year, score
> tom, 1995, 88
> rick, 1994, 90
> mary, 2000, 97
> tom, 1998, 60
> mary, 1998,100
>
> I shall have
> ID, year, score
> tom, 1995, 88
> rick, 1994, 90
> mary, 1998,100
>
> Thanks,
> Richard
>
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>
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-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O