specification of corAR1()
On Wed, 2011-08-10 at 10:07 -0700, array chip wrote:
Hi all, I am struggling to learn to use corAR1() correlation structure. Let me use the Machines data set from nlme package as an example: I added a time variable to create a new dataset:
Machines2<-cbind(Machines, time=c(1,2,3))
This one runs without any problem:
lme(score~Machine,data=Machines2,random=list(Worker=pdSymm(~0+Machine)),correlation=corAR1())
That's not what the first argument of corAR1() is for. Not the first time that has caught someone out (there's at least you and me!). G
But all of the following generated the same error message:
lme(score~Machine,data=Machines2,random=list(Worker=pdSymm(~0+Machine)),correlation=corAR1(~time)) lme(score~Machine,data=Machines2,random=list(Worker=pdSymm(~0+Machine)),correlation=corAR1(~time|Worker)) lme(score~Machine,data=Machines2,random=list(Worker=pdSymm(~0+Machine)),correlation=corAR1(~time|Worker/Machine))
"Error in abs(value) : Non-numeric argument to mathematical function" Did I misunderstand something here? Thanks very much! John
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