[R] Asymmetrical ANOVA / contrasts

[Joachim Claudet]

Dear all,

I have problems to code contrasts for performing an asymmetrical anova 
with aov(). I am using aov() because I want to get the Mean Squares for 
further analyses. I didn't find any solution to my problem in the help 
files of functions aov(), contrasts(), C(), etc.
Let's say I have three locations, one with treatment P, and two with 
treatment C:
 > loc=factor(c(P1,P1,P1,P1,P1,C1,C1,C1,C1,C1,C2,C2,C2,C2,C2))
And here is my variable:
 > X=c(21,23,34,32,23,9,4,5,6,8,3,2,8,7,6)
I want to test the effect of location P versus location C
Here is what I have done:
 > contrasts(loc)=contr.treatment(3)
 > aov(X~C(loc,c(2,-1,-1)))
This gives me exactly the same result as if I was doing simply 
aov(X~loc) without first coding for the contrasts.
I have also tried:
 > aov(X~loc,contrasts=contrasts(loc))

Could somebody tell me how to do?
Any help would be greatly appreciated.
Thanks,
Joachim Claudet.

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Joachim Claudet

PhD

EPHE - CNRS FRE 2935
52, avenue Paul Alduy
66860 Perpignan cedex
Tel : 33 4 68662055
Fax : 33 4 68503686


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