[R] Aggregating a List

Paul Boutros pcboutro at engmail.uwaterloo.ca
Wed Nov 6 20:20:47 CET 2002

Hi all,

There must be a really obvious R solution to this, but I can't figure out
how to aggregate a list.  For instance, if I read.table the following from
a file:
	Val1	Val2
A	3	4
A	5	6
B	4	4

I would like to take the mean (or median) across any/all rows of type "A"
to end up with the structure:

	Val1	Val2
A	4	5
B	4	4

in this case.  How would I go about doign that w/o doing a loop or putting
into a DB and using SQL to do this?

Thanks for any suggestions, or pointers at appropriate functions I should
be reading the documentation on.


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