[R] How to get Greenhouse-Geisser epsilons from anova?

Peter Dalgaard p.dalgaard at biostat.ku.dk
Thu Dec 4 23:23:32 CET 2008


Skotara wrote:
> Dear all,
> 
> I apologize for my basic question.
> I try to calculate an anova for repeated measurements with 3 factors 
> (A,B,C) having 2, 2, and 7 levels.
> or with an additional fourth between subjects factor D.
> Everything works fine using
> aov(val ~ A*B*C  + Error(subject/ (A*B*C) ) )  or
> aov(val ~ (D*A*B*C)  + Error(subject/(A*B*C)) + D )
> val, A, B, C, D and subject are columns in a data.frame.
> 
> How can I get the estimated Greenhouse-Geisser and Huynh-Feldt epsilons?
> I know Peter Dalgaard described it in R-News Vol. 7/2, October 2007. 
> However, unfortunately I am not able to apply that using my data...

Why? It is supposed to work. You just need to work out the X and M 
specification for the relevant error strata and set test="Spherical" for 
anova.mlm, or work out the T contrast matrix explicitly if that suits 
your temper better.

> Furthermore, I am still confused of how SPSS calculates the epsilons 
> since it is mentioned that perhaps there are any errors in SPSS??
> 
> I would be glad if anyone could help me!
> I am looking forward to hearing from you!
> 
> Thank you!
> Nils
> 
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-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907



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