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Glimmix Repeated Measure Error

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New Contributor
Posts: 2

Glimmix Repeated Measure Error

Can anyone tell me what the following error means? 

 

WARNING: The R matrix depends on observation order within subjects. Omitting observations from
the analysis because of missing values can affect this matrix. Consider using a
classification effect in the RANDOM _RESIDUAL_ statement to determine ordering in the R
matrix.

 

I am attempting to run repeated measures on some data. The design was 20 animals blocked into light and heavy bodyweights, then assigned to 1 of 2 treatments withing each block. The animals had biopsies at 5 time points and gene expression was measured on 8 genes at each point. Attached is the SAS input as well as the output. I am not sure my denominator DF are correct and this may be associated with the error? Any help would be greatly appreciated.

SAS Employee
Posts: 17

Re: Glimmix Repeated Measure Error

When you have missing observations on the RANDOM _RESIDUAL_ statement in GLIMMIX then the procedure generates the warning message. Considering change the RANDOM _RESIDUAL_ to -

 

Proc glimmix data = JessicaPCR;

Class ID TRT BLOCK DAY;

Model AMPK = TRT|DAY/ddfm = KR;

random intercept / subject=BLOCK;

random intercept / subject=ID*TRT;

random day /subject = ID*TRT type=arh(1) residual;

LSMEANS TRT|DAY/ pdiff lines;

nloptions tech=nrridg;

Run;

 

The above RANDOM statement should make note go away.

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