Nils Skotara wrote:
Thank you, this helped me a lot!
All within effects and interactions work well!
Sorry, but I still could not get how to include the between factor..
If I include D with 2 levels, then myma is 24 by 28. (another 12 by 28 for the
second group of subjects.)
mlmfitD <- lm(myma~D) is no problem,
but whatever I tried afterwards did not seem logical to me.
I am afraid I do not understand how to include the between factor.
I cannot include ~D into M or X because it has length 24 whereas the other
factors have 28...
Just do the same as before, but comparing mlmfitD to mlmfit:
anova(mlmfitD, mlmfit, X=~A+B, M=~A+B+C)
# or anova(mlmfitD, mlmfit, X=~1, M=~C), as long as things are balanced
gives the D:C interaction test (by testing whether the C contrasts
depend on D). The four-factor interaction is
anova(mlmfitD, mlmfit, X=~(A+B+C)^2, M=~A*B*C)
Zitat von Peter Dalgaard <[EMAIL PROTECTED]>:
Skotara wrote:
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
dd$C is not a factor with that construction. It works for me after
dd$C <- factor(dd$C)
(The other message is nasty, though. It's slightly different in R-patched:
> anova(mlmfit, mlmfit0, X= ~A+B, M = ~A+C+B, idata = dd,
test="Spherical")
Error in solve.default(Psi, B) :
system is computationally singular: reciprocal condition number =
2.17955e-34
but it shouldn't happen...
Looks like it is a failure of the internal Thin.row function. Ick!
)
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...
The "within" interactions should be straightforward, e.g.
M=~A*B*C
X=~A*B*C-A:B:C
etc.
The within/between interactions are otained from the similar tests of
the between factor(s)
e.g.
mlmfitD <- lm(myma~D)
and then
anova(mlmfitD, mlmfit,....)
--
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
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
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