Programming the statistical procedures from SAS

need to sort by subject in proc glimmix?

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need to sort by subject in proc glimmix?

Hi,

I know that often with clustered data it is necessary to sort by the cluster ID. I have a subject defined by an ID variable (random _residual_/ subject=ID type=sp(exp) (X Y)Smiley Wink that is a classification variable (class id; below proc glimmix statement). Because it is a classification variable, I do not think I need to sort by it before running glimmix. I have tried it both ways (with and without invoking proc sort by id). The fixed effects and their SE are the same but my covariance parameter estimates differ slightly. Is this indicative of needing to sort? I ask (instead of just always sorting) because I do not want to have to re-run several previous analyses unless necessary. Thanks,Seth
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