I have 1000 persons data with 5 years' annual bone mineral density (BMD) measurement. Now I want to get the bone mineral density (BMD) change rate per year. Because this is longitudinal data, I think I should use proc mixed. My data is like: id visit group bmd 1 0(baseline) a 1.01 1 1 a 1.00 1 2 a 1.00 1 3 a 0.99 1 4 a 0.98 1 5 a 0.96 2 0(baseline) b 1.07 2 1 b 1.06 2 2 b 1.04 2 3 b 0.99 2 4 b 0.95 2 5 b 0.93 ...... My code is : PROC MIXED DATA=mydaa noclprint; CLASS id visit group; MODEL bmd = visit group group*visit / SOLUTION CL DDFM=KR OUTPM=aaa; REPEATED visit / SUBJECT=id TYPE=UN R RCORR; RUN; Is this code correct? and where can I get the change rate in the output? I read one paper said the estimate is the change rate, but the numbers are positive (the change rate should negative). And I plot the result like this: PROC SGPLOT DATA=aaa; SERIES x = visit y = pred / GROUP = group MARKERS; RUN; The plot looks correct. But how can I get the numbers for the slop? Thank you very much for your help.
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