The different answers reflect a lack of symmetry in the data set. The standard "A+B" anova evaluates the effect of A by itself and B given A. The other evalutes the effect of B by itself plus A given B. They answer different questions. If you want the same answer from "A+B" as from "B+A", you have to be clearer about what you want. For more discussion of that, see any good book on analysis of variance, including discussions of Types II and III sums of squares, e.g., from "www.r-project.org" -> search -> R site search.

Judging from what they did, it seems apparent that the R developers and the S and S-Plus developers before them felt that it was best to report results in this way.

hope this helps. spencer graves

Mahbub Latif wrote:
Hi,

I use lme to fit models like

R> res1 <- lme(y~A+B, data=mydata, random=~1|subject)
R> res2 <- lme(y~B+A, data=mydata, random=~1|subject)

(only difference between these two models are the
sequence in which the indep variables are written in
formula)

where y is continuous and A, B, and subject are
factors. To get ANOVA table I used

R> anova(res1)
R> anova(res2)

and found ANOVA tables corresponding to these two
models are different. Is there any way I can get
similar ANOVA tables from lme objects of this type?

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