[R] Odp: by group problem

Petr PIKAL
Fri, 31 Aug 2007 13:15:29 -0000

Hi

> I am working with census data.  My columns of interest are...
>
> PercentOld - the percentage of people in each county that are over 65
> County - the county in each state
> State - the state in the US
>
> There are about 3100 rows, with each row corresponding to a county
within a state.
>
> I want to return the top five "PercentOld" by state.  But I want
the
County
> and the Value.
>
> I tried this...
>
> topN <- function(column, n=5)
>   {
>     column <- sort(column, decreasing=T)
>     return(column[1:n])
>   }
> top5PerState <- tapply(data$percentOld, data$STATE, topN)

Try

aggregate(data$PercentOld, list(data$State, data$County), topN)

Regards
Petr


>
> But this only returns the value for "percentOld" per state, I
also want
the
> corresponding County.
>
> I think I'm close, but I just can't get it...
>
> Thanks
>
> cn
>
>    [[alternative HTML version deleted]]
>
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