aggregate() runs out of memory

Hi:

This should give you some idea of what Steve is talking about:

library(data.table)
dt <- data.table(x = sample(100000, 10000000, replace = TRUE),
                  y = rnorm(10000000), key = "x")
dt[, .N, by = x]
system.time(dt[, .N, by = x])

...on my system, dual core 8Gb RAM running Win7 64-bit,

system.time(dt[, .N, by = x])

   user  system elapsed
   0.12    0.02    0.14

.N is an optimized function to find the number of rows of each data subset.
Much faster than aggregate(). It might take a little longer because you
have more columns that suck up space, but you get the idea. It's also about
5-6 times faster if you set a key variable in the data table than if you
don't.

Dennis

On Fri, Sep 14, 2012 at 12:26 PM, Sam Steingold <sds at gnu.org> wrote:

I have a large data.frame Z (2,424,185,944 bytes, 10,256,441 rows, 17
columns).
I want to get the result of
table(aggregate(Z$V1, FUN = length, by = list(id=Z$V2))$x)
alas, aggregate has been running for ~30 minute, RSS is 14G, VIRT is
24.3G, and no end in sight.
both V1 and V2 are characters (not factors).
Is there anything I could do to speed this up?
Thanks.

--
Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X
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