Hi: Here's a plyr solution:
library(plyr) dg <- data.frame(x1 = rep(1:2, c(10, 15)), x2 = 1:25) f <- function(x) head(rev(sort(x)), 5) > ddply(dg, 'x1', summarise, x2 = f(x2)) x1 x2 1 1 10 2 1 9 3 1 8 4 1 7 5 1 6 6 2 25 7 2 24 8 2 23 9 2 22 10 2 21 HTH, Dennis On Fri, Dec 10, 2010 at 6:18 AM, andrija djurovic <djandr...@gmail.com>wrote: > Hi R-help, > > > > I am trying to find a way to select five highest values in data frame > according some variable. I will demonstrate: > > c > > X1 X2 > > 1 1 1 > > 2 1 2 > > 3 1 3 > > 4 1 4 > > 5 1 5 > > 6 1 6 > > 7 1 7 > > 8 1 8 > > 9 1 9 > > 10 1 10 > > 11 2 11 > > 12 2 12 > > 13 2 13 > > 14 2 14 > > 15 2 15 > > 16 2 16 > > 17 2 17 > > 18 2 18 > > 19 2 19 > > 20 2 20 > > 21 2 21 > > 22 2 22 > > 23 2 23 > > 24 2 24 > > 25 2 25 > > > > So I would like to select a rows with higest values of X2 inside X1. > Expected result should be: > > X1 X2 > > 1 10 > > 1 9 > > 1 8 > > 1 7 > > 1 6 > > 2 25 > > 2 24 > > 2 23 > > 2 22 > > 2 21 > > > > I first oreded the data frame using > > c=c[with(c,order(X1,-X2)),] > > but I need a help to select highes five. It is easy to select when I have > just 2 unique values of X1 but what is if I have 500 unique values in X1? > > > > Thanks > > Andrija > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
