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2009 Dec 03
4
Two-way/Three-way sum.
Hi R Users, I'm wondering how can I calculate two (or three) way sum of a variable. A sample data is: State Month Year Value NC Jan 1996 1 NC Jan 1996 2 NC Feb 1997 2 NC Feb 1997 3 NC Mar 1998 3 NC Mar 1998 4 NY Jan 1996 4 NY Jan 1996 5 NY Feb 1997 5 NY Feb 1997 6 NY Mar 1998 6 NY Mar 1998 7 I'm trying to sum up "value" column by State*Month and by State*Month*Year. Also, I