[R] the first and last case

From: Mauricio Cardeal <mcardeal_at_ufba.br>
Date: Wed 26 Jul 2006 - 22:22:19 EST


Hi all

Sometime ago I asked for a solution about how to aggregate data and the help was wonderful. Now, IŽd like to know how to extract for each individual case below the first and the last observation to obtain this:

ind y
1 8
1 9
2 7
2 11
3 9
3 10
4 8
4 5

# Below the example:

ind <- c(1,1,1,2,2,3,3,3,4,4,4,4)
y <- c(8,10,9,7,11,9,9,10,8,7,6,5)
dat <- as.data.frame(cbind(ind,y))
dat
attach(dat)

mean.ind <- aggregate(dat$y, by=list(dat$ind), mean) mean.ind

Thanks
Mauricio



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