[R] Grouping data in a data frame: is there an efficient way to do it?

I have a data frame with about 10^6 rows; I want to group the data according to entries in one of the columns and do something with it. For instance, suppose I want to count up the number of elements in each group. I tried something like aggregate(my.df$my.field, list(my.df$my.field), length) but

Re: [R] Grouping data in a data frame: is there an efficient way to do it?

have a multiprocessor system with the doMC package to run iterations in parallel. There's an example here: http://blog.revolution-computing.com/2009/08/blockprocessing-a-data-frame-with-isplit.html Hope this helps, # David Smith On Wed, Sep 2, 2009 at 3:39 PM, Leo Alekseyev dnqu...@gmail.com