[R] vector-factor operation

Thomas Lumley tlumley at u.washington.edu
Fri Apr 14 18:09:00 CEST 2006

On Fri, 14 Apr 2006, Murray Jorgensen wrote:

> I found myself wanting to average a vector [vec] within each level of a
> factor [Fac], returning a vector of the same length as vec. After a
> while I realised that
> lm1 <- lm(vec ~ Fac)
> fitted(lm1)
> did what I want.
> But there must be another way to do this, and it would be good to be
> able to apply other functions than mean() in this way.


and, yes, it can take a different function as an argument.


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