topic Doubly repeated measures with GLIMMIX in Statistical Procedures

Doubly repeated measures with GLIMMIX

Bhupi — Tue, 20 Aug 2013 22:00:34 GMT

Hi,

I want to set up doubly repeated measures using GLIMMIX but I haven't used GLIMMIX for repeated measures. The model so far I have now is

Proc glimmix data = wheat namelen=200 plots=residualpanel (conditional marginal);

class Year Block Plot Cultivar Nrate Sampling;

model DM = Nrate|Cultivar|Part|Sampling/ddfm=kr ;

Random Year Block(Year);

run;

It's split-plot design with Nrate as whole plot (3 levels) and cultivar as split-plot (4 levels). Number of years are 3 and blocks (replications) are four. So, each year there were 48 plots. From each plot (48), plant samples were taken and divided into two "Part" (Head and stem). Their dry matter (DM) was measured. These samples were taken four times (Sampling) during the season.

The two parts (head and stem) have residuals effect and so is from sampling. Therefore Part and Sampling should be set as repeated measures but I don't know how to do it.

Thanks,

Bhupinder

Re: Doubly repeated measures with GLIMMIX

SteveDenham — Wed, 21 Aug 2013 19:27:52 GMT

Hey Bhupinder,

Check out Example 41.5 in the PROC GLIMMIX documentation. It gives a way to jointly model variables of different distributions. In your case, you can set up a joint model, but specify the same distribution. This is as close to the Kronecker doubly repeated measures method in MIXED as you are going to be able to do in GLIMMIX.

If the doubly repeated measures were nested (say week within month, or month and season), I'd say create a compound measure and sort out the comparisons using LSMESTIMATE statements.

Steve Denham

Re: Doubly repeated measures with GLIMMIX

Bhupi — Thu, 22 Aug 2013 20:10:37 GMT

Hello Steve,

Thanks for the direction. It seems the possible solution is to create multiple G-side effects but only one R-side random effect.

Bhupinder

Re: Doubly repeated measures with GLIMMIX

SteveDenham — Fri, 23 Aug 2013 15:03:08 GMT

Good call on the multiple G-side. This should do it, especially if you get the subject= option correct.

Steve Denham