I'm trying to run a simple one-way ANCOVA with the lmer function in R
package lme4, but have encountered some conceptual problem. The data
file MyData.txt is like this:
Group Subj Cov Resp
A 1 3.90 4.05
A 2 4.05 4.25
A 3 4.25 3.60
A 4 3.60 4.20
A 5 4.20 4.05
A 6 4.05 3.85
B 7 3.85 4.15
B 8 4.15 4.60
B 9 4.60 4.15
B 10 4.15 4.40
B 11 4.40 3.35
B 12 3.35 3.80
B 13 3.80 3.90
Since I would like to treat subject (Subj) as a random factor, my one-
way ANCOVA (with covariate, Cov) is:
TestData=read.table("MyData.txt", header=T);
m1 <- lmer(Resp ~ Group * Cov + (1 | Subj), TestData)
but I got the following error message:
Error in lmerFactorList(formula, mf, fltype) :
number of levels in grouping factor(s) 'Subj' is too large
Do I have some misconception about the model?
Thank you very much.
Gang
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