[R] the first and last case

[Jacques VESLOT]

do.call(rbind,lapply(split(dat, dat$ind), function(x) x[c(1,nrow(x)),]))
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Jacques VESLOT

CNRS UMR 8090
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Mauricio Cardeal a écrit :
> Hi all
> 
> Sometime ago I asked for a solution about how to aggregate data and the 
> help was wonderful. Now, I´d 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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