[R] group mean, minus each row's value

[Greg Snow]

Try:

> w <- ave(x,g)
> n <- ave(x,g, FUN=length)
> wnew <- (w*n - x)/(n-1)

Or

> s <- ave(x,g, FUN=sum)
> n <- ave(x,g, FUN=length)
> wnew <- (s-x)/(n-1)

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at intermountainmail.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 Casey Klofstad
> Sent: Tuesday, November 13, 2007 8:45 AM
> To: r-help at r-project.org
> Subject: [R] group mean, minus each row's value
> 
> I used the following to assign each row the group average, 
> where w is the new group average variable, x is the variabale 
> to be averaged, and g is the nominal group indicator:
> 
> w <- ave(x,g)
> 
> Now I want to calculate the group average, but WITHOUT each 
> row's value of x. Is there an easy way to do this? I'm sure 
> I'm missing something obvious here, but for the life of me I 
> can't figure it out.
> 
> Thanks!
> --
> Casey A. Klofstad
> University of Miami
> Department of Political Science
> Coral Gables, FL
> 
> klofstad at gmail.com
> http://moya.bus.miami.edu/~cklofstad
> 
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