Hi, I ran into some problems with adding a continous covariate in repeated measures using proc mixed, and there is not much information on the internet. The situation is like measuring weight gain over time and I want to add initial weights as covariate, then compare weight gain between time points. Analysis ran well without covariate, however, when I added in the covariate, lsmeans of weight gain at different time points were not estimatable. here are the codes I used data survey; input id gain time blk wt; cards; 1 6.00 1 2 90 1 4.80 1 1 83 2 5.80 1 2 74 2 4.40 1 1 87 1 5.25 2 2 90 1 4.00 2 1 83 2 5.00 2 2 74 2 4.70 2 1 87 1 5.25 3 2 90 1 4.50 3 1 83 2 4.25 3 2 74 2 5.10 3 1 87 ; proc mixed data=survey; class id time blk; model gain = time blk id(blk) wt; repeated time / type = ar(1) subject = id(blk); lsmeans time / pdiff adjust = bon; run; Can anyone help? Thanks.
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