NLMIXED and GEE

Statooed — Sun, 25 Mar 2012 14:14:21 GMT

Dear All,

While using PROC NLMIXED or GEE is there a specific way the clustering variable should be coded.

Does coding effects the results. For instance say I have subject=PHYSICIAN in my PROC NLMIXED option or repeated subject=PHYSICIAN in PROC GEE will it effect my results or will it create issues with convergence if I code PHYSICIAN as (1,2,3,4) or PHYSICIAN as (64055, 65471,56432).

If it does effect then how can I change the coding scheme for a variable in SAS. As currently my PHYSICIAN is coded with 5 digit numeric codes (eg physician A has code 64055, physican B has code 65275 and so on). There are 58 physicians (clusters) and the cluster size (number of patients being treated by each physician) varies from 1 to 39.

Looking forward for your ocmments and suggesitons.

Best Regards,

Tasneem

NLMIXED and GEE

SteveDenham — Mon, 26 Mar 2012 11:50:44 GMT

So long as the clustering variable is explicitly included in the CLASS statement, it should be OK. I worry somewhat about the 'repeated' statement, but I believe you will be using PHYSICIAN as in SUBJECT=PHYSICIAN part. If not, then careful consideration needs to be made as to the possible covariance structures and the effect of coding on them.

Steve Denham

topic NLMIXED and GEE in SAS Procedures

NLMIXED and GEE

NLMIXED and GEE