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jrrbc
2009 Sep 02
4
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 it seems to be very slow. Likewise,
the split() function was slow (I killed it before it completed).