That didn't work for me...
Here's some data to help with a solution.
data <- NULL
data$state <- c(rep("Illinois", 10), rep("Wisconsin", 10))
data$county <- c("Adams", "Brown", "Bureau", "Cass", "Champaign",
"Christian", "Coles", "De Witt", "Douglas", "Edgar",
"Adams", "Ashland", "Barron", "Bayfield", "Buffalo",
"Burnett", "Chippewa", "Clark", "Columbia", "Crawford")
data$percentOld <- c(17.554849, 16.826594, 18.196593, 17.139242, 8.743823,
17.862746, 13.747967, 16.626302, 15.258940, 18.984435,
19.347022, 17.814436, 16.903067, 17.632781, 16.659305,
20.337817, 14.293354, 17.252820, 15.647179, 16.825596)
return something like this...
$Illinois
"Edgar"
18.984435
"Bureau"
18.196593
...
$Wisconsin
"Burnett"
20.33782
"Adams"
19.34702
...
My Solution gives...
topN <- function(column, n=5)
{
column <- sort(column, decreasing=T)
return(column[1:n])
}
tapply(data$percentOld, data$state, topN)
$Illinois
[1] 18.98444 18.19659 17.86275 17.55485 17.13924
$Wisconsin
[1] 20.33782 19.34702 17.81444 17.63278 17.25282
I get an error with this try...
aggregate(data$percentOld, list(data$state, data$county), topN)
Error in aggregate.data.frame(as.data.frame(x), ...) :
'FUN' must always return a scalar
Thanks
cn
________________________________
From: Petr PIKAL [mailto:[EMAIL PROTECTED]
Sent: Fri 8/31/2007 8:15 AM
To: Cory Nissen
Cc: r-help@stat.math.ethz.ch
Subject: Odp: [R] by group problem
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
>
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>
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