How to get Greenhouse-Geisser epsilons from anova?
Dear Nils, You might also take a look at the Anova() function in the car package, which though less flexible than anova() should get you the tests that you want more simply. ?Anova has an example of a repeated-measures ANOVA with two within-subject and two between-subject factors. I hope that this helps, John ------------------------------ John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Skotara
Sent: December-05-08 8:40 AM
To: Peter Dalgaard; r-help at r-project.org
Subject: Re: [R] How to get Greenhouse-Geisser epsilons from anova?
Dear Mr. Daalgard.
thank you very much for your reply, it helped me to progress a bit.
The following works fine:
dd <- expand.grid(C = 1:7, B= c("r", "l"), A= c("c", "f"))
myma <- as.matrix(myma) #myma is a 12 by 28 list
mlmfit <- lm(myma~1)
mlmfit0 <- update(mlmfit, ~0)
anova(mlmfit, mlmfit0, X= ~C+B, M = ~A+C+B, idata = dd,
test="Spherical"), which tests the main effect of A.
anova(mlmfit, mlmfit0, X= ~A+C, M = ~A+C+B, idata = dd,
test="Spherical"), which tests the main effect of B.
However, I can not figure out how this works for the other effects.
If I try:
anova(mlmfit, mlmfit0, X= ~A+B, M = ~A+C+B, idata = dd,
test="Spherical")
I get:
Fehler in function (object, ..., test = c("Pillai", "Wilks",
"Hotelling-Lawley", :
residuals have rank 1 < 4
I also don't know how I can calculate the various interactions..
My read is I should change the second argument mlmfit0, too, but I can't
figure out how...
Do you know what to do?
Thank you very much!
Peter Dalgaard schrieb:
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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______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.