[R] How to specify arguments in lme() ?
w jj
jiajiehere at hotmail.com
Thu Jan 18 16:25:59 CET 2007
Hi,
I have a question about the function lme() in R.
I have a 2*2*3 layout with some missing data (labelled as *). These 3
factors are labelled as A,B,C, the response is Score. The layout is as
follows:-
A B C Score
1 1 1 5
1 1 2 *
1 1 3 1
1 2 1 4
1 2 2 4
1 2 3 *
2 1 1 3
2 1 2 *
2 1 3 4
2 2 1 2
2 2 2 *
2 2 3 5
Suppose these data are stored in a data frame called "test".
If all these 3 factors are fixed, then I can fit a model without the 3-way
interaction as:-
fit1<-lm(Score~A*B+A*C+B*C,data=test)
If one of these factors, say A, is a random effect variable, then I need to
fit a mixed effect model using lme(). I have read the R documention on
lme(), but I am still not clear how to specify the random argument. I tried
to do:-
fit2<-lme(Score~A*B+A*C+B*C,data=test,random=~A, na.action=na.pass)
but the system give a message as follows:-
Error in getGroups.data.frame(dataMix, groups) :
Invalid formula for groups
So how should I specify the arguments?
Thank you very much for your help!
Jiajie
More information about the R-help
mailing list