How do I get a block diagonal covariance matrix, V, in SAS PROC MIXED or PROC GLIMMIX?

Lyson — Thu, 18 Jul 2024 13:09:24 GMT

Hi friends,

I am trying to estimate a linear mixed model in SAS using prc mixed or proc glimmix. I have 3 categorical factors A, B and C where factor C is assumed random, and A,B are fixed. My data set looks like this:

The syntaxes that I am exploring are:

a) PROC GLIMMIX

proc glimmix data=FFRgroup outdesign=XZ;;
class factorA factorB factorC  groupA groupB groupC rep;
model yield= groupA | groupB / ddfm=satterthwaite;
random factorC factorA*factorC  factorB*factorC factorA*factorB*factorC /  V;
lsmeans groupA | groupB   / pdiff cl alpha=0.05 ;
Title "FFR Model";
run;

whch displays the following V matrix,

b) PROC MIXED:

proc mixed data=FFRgroup ;
class factorA factorB factorC  groupA groupB groupC rep;
model yield= groupA | groupB / ddfm=satterthwaite;
random factorC factorA*factorC  factorB*factorC factorA*factorB*factorC /  V;
lsmeans groupA | groupB   / pdiff cl alpha=0.05 ;
Title "FFR Model";
run;

displays the following V matrix,

What could be the problem with these two approaches not producing the covariance structure that aligns with the model in question (block diagonal)?

Thank you in advance for your assistance folks.

Re: How do I get a block diagonal covariance matrix, V, in SAS PROC MIXED or PROC GLIMMIX?

Rick_SAS — Fri, 19 Jul 2024 12:52:40 GMT

Dup of Solved: How do i get a block diagonal covariance matrix, V, in SAS Proc Mixed ... - SAS Support Communities

topic Re: How do I get a block diagonal covariance matrix, V, in SAS PROC MIXED or PROC GLIMMIX? in Statistical Procedures

How do I get a block diagonal covariance matrix, V, in SAS PROC MIXED or PROC GLIMMIX?

Re: How do I get a block diagonal covariance matrix, V, in SAS PROC MIXED or PROC GLIMMIX?