Frank, Is it a windows machine as well? And could you try to use `debugonce` to find out the line(s) where it's slow?
Arun On Friday, August 16, 2013 at 12:34 PM, Frank Erickson wrote: > I get similar timings to arun, with the data.table call being a lot slower > than the other timings. If data.table is not optimized for that .SD > expression, perhaps that is okay because, as Arun pointed out, there are > alternatives.. I can't guess why it would perform differently on different > hardware, though... > > # alternatives: > a <- dt1[dt1[, .I[.N], by='Date']$V1] > b <- dt1[J(unique(Date)),,mult='last'] # a little slower > d <- dt1[, .SD[.N], by='Date'] # 600x slower; it would take ages to benchmark > identical(a,b) # true > identical(a,d) # false > identical(as.data.frame(d),as.data.frame(a)) # true > > --Frank >
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