Hi all,
I was wondering if someone could help me designing a contrast matrix when
you have a continuous variable (Days).
My model looks like this:
model<-lme(Y~A*B*Days, data=data_over_time)
The factor A has two levels (A1 and A2) and factor B has three levels (B1,
B2, and B3). I measured the response variable Y every two or three days over
70 days (Days).
I need to look at only a few comparisons over the 70 days such us:
A1 and B1 vs A2 and B1,
A2 and B2 vs A2 and B1,
A1 and B2 vs A2 and B2
I could use the function contrast from the package contrast to design the
matrix with all three comparisons. I know how to do it for specific days at a
time. This would give me the first comparison for day 1.
a=contrast(model,
a=list(A='A1',B='B1',Days=1),
b=list(A='A2',B='B1',Days=1)
)
However, I need to run the comparison over the 70 days not at
individual time points at a time.
I was wondering if someone could help me designing this contrast matrix.
Any help would be much appreciated
Cheers
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