[datatable-help] Order of DT after non-keyed by

[Joseph Voelkel]

Here is a simple example of a simple question:

dt<-data.table(a=rep(1:5,1:5),b=1,c=rep(1:3,5))
dt
dt[,seq_along(b),by=a] # expected behavior (note: dt is already in order of a)
setkey(dt,c) # to sort by c
dt
dt[,seq_along(b),by=a] # expected behavior? Appears to be in order of unique(dt$a)

Thanks,

Joe Voelkel
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