[R] (unclassified?) Help Question
David Winsemius
dwinsemius at comcast.net
Sat Jul 16 22:42:30 CEST 2011
On Jul 16, 2011, at 4:08 PM, Lars Bishop wrote:
> Dear List,
>
> I'd appreciate you guidance for obtaining the desired result shown
> below, by combining tapply(x, g, mean) and g in the example.
>
> Basically, I'm trying to create a vector whose values are based on the
> result from tapply(x, g, mean) but that follow the pattern and length
> given by the factor g.
What does that mean? The length of g is 10 and there are 4 unique
values. How are we supposed to get 8 categories?
> length(g)
[1] 10
> length(unique(g))
[1] 4
--
David.
> Of course I'm looking for a generic solution
> (i.e, not something that just work for this particualr case).
>
> set.seed(1)
> f1 <- gl(2, 1, 10, labels=c("M", "F"))
> f2 <- gl(2, 2, 10, labels=c("H", "L"))
> x <- rnorm(10)
> d <- data.frame(f1, f2, x)
> g <- interaction(f1, f2)
> tapply(x, g, mean)
>> M.H F.H M.L F.L
>> 0.0929451 -0.3140711 -0.1740998 1.1668028
> g
>> [1] M.H F.H M.L F.L M.H F.H M.L F.L M.H F.H
>> Levels: M.H F.H M.L F.L
>
> Desired result:
>
> x
>> [1] 0.0929451 -0.3140711 -0.1740998 1.1668028 0.0929451
>> -0.3140711 -0.1740998
>> [8] 1.1668028
>
>
> Thanks for any help!
> Lars.
>
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David Winsemius, MD
West Hartford, CT
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