[R] how to select rows per subset in a data frame that are max. w.r.t. a column

Ivan Calandra ivan.calandra at uni-hamburg.de
Tue May 18 11:12:07 CEST 2010


Maybe it's just me but I don't understand what you're trying to do.
Isn't maxValues what you need?
Providing a reproducible example with your data (using the function 
dput), the desired output, and the code you've tried would really help!


Le 5/18/2010 10:58, Tim Van den Bulcke a écrit :
> Hi,
> I'd like to select one row in a data frame per subset which is maximal for a
> particular value. I'm pretty close to the solution in the sense that I can
> easily select the maximal values per subset using "aggregate", but I can't
> really figure out how to select the rows in the original data frame that are
> associated with these maximal values.
> library(stats)
> # this returns the list with maximal values for breaks per wool/tension
> subset
> maxValues = aggregate(warpbreaks$breaks, list(wool = wool, tension =
> tension), max)
> # now i'd like the subset of the rows in warpbreaks that are associated with
> these maximal values
> Thank you in advance!
> Tim.
> 	[[alternative HTML version deleted]]
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