[R] Two-way/Three-way sum.

[Greg Snow]

?tapply

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Peng Cai
> Sent: Thursday, December 03, 2009 11:50 AM
> To: r-help at r-project.org
> Subject: [R] 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 may need to calculate mean value along with "sum".
> 
> Any help would be greatly appreciated,
> 
> Thanks,
> Peng
> 
> 	[[alternative HTML version deleted]]
> 
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