[R] apply a function over a factor

[Dimitris Rizopoulos]

have a look at ?ave(), e.g.,

A <- 1:10
B <- factor(c(1,2,2,4,4,4,7,7,7,7))

ave(A, B)


I hope it helps.

Best,
Dimitris


faridamsb at gmail.com wrote:
> Dear R experts,
> 
> I would like to substitute the values of a vector, say A, with the average  
> values taken over a factor
> 
> For example, lets assume
> 
> 
> A
> 
> [1] 1 2 3 4 5 6 7 8 9 10
> 
> B
> 
> [1] 1 2 2 4 4 4 7 7 7 7
> Levels: 1 2 4 7
> 
> I need to have
> 
> 1.0 2.5 2.5 5.0 5.0 5.0 8.5 8.5 8.5 8.5 8.5
> 
> Thank you
> 
> 	[[alternative HTML version deleted]]
> 
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> 

-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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