..by some (extensive) trial and error reordering the contrast matrix
and the
reference level
i figured it out myself -
for anyone who might find this helpful searching for a similar
contrast in
the future:
this should be the right one:
c2<-rbind("fac2-effect in A"=c(0,1,0,0,0,0,0,0),
"fac2-effect in B"=c(0,1,0,0,0,1,0,0),
"fac2-effect in C"=c(0,1,0,0,0,0,1,0),
"fac2-effect in D"=c(0,1,0,0,0,0,0,1),
"fac2-effect, A*B"=c(0,0,0,0,0,1,0,0),
"fac2-effect, A*C"=c(0,0,0,0,0,0,1,0),
"fac2-effect, A*D"=c(0,0,0,0,0,0,0,1),
"fac2-effect, B*C"=c(0,0,0,0,0,-1,1,0),
"fac2-effect, B*D"=c(0,0,0,0,0,-1,0,1),
"fac2-effect, C*D"=c(0,0,0,0,0,0,-1,1))
summary(glht(mod,c2))
Kay Cichini wrote:
hello,
i was shortly asking the list for help with some interaction
contrasts
(see below) for which
i had to change the reference level of the model "on the fly" (i
read a
post that this is possible in
multcomp).
if someone has a clue how this is coded in multcomp; glht() -
please point
me there.
yours,
kay
Kay Cichini wrote:
hello list,
i'd very much appreciate help with setting up the
contrast for a 2-factorial crossed design.
here is a toy example:
library(multcomp)
dat<-data.frame(fac1=gl(4,8,labels=LETTERS[1:4]),
fac2=rep(c("I","II"),16),y=rnorm(32,1,1))
mod<-lm(y~fac1*fac2,data=dat)
## the contrasts i'm interressted in:
c1<-rbind("fac2-effect in A"=c(0,1,0,0,0,0,0,0),
"fac2-effect in B"=c(0,1,0,0,0,1,0,0),
"fac2-effect in C"=c(0,1,0,0,0,0,1,0),
"fac2-effect in D"=c(0,1,0,0,0,0,0,1),
"fac2-effect, A*B"=c(0,0,0,0,0,1,0,0),
"fac2-effect, A*C"=c(0,0,0,0,0,0,1,0),
"fac2-effect, A*D"=c(0,0,0,0,0,0,0,1))
summary(glht(mod,c1))
## now i want to add the remaining combinations
## "fac2, B*C"
## "fac2, B*D"
## "fac2, C*D"
## to the simultanous tests to see whether the effects
## of fac2 within the levels of fac1 differ between
## each combination of the levels of fac1, or not ??
thanks for any advise!
yours,
kay
-----
------------------------
Kay Cichini
Postgraduate student
Institute of Botany
Univ. of Innsbruck
------------------------
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