topic Proc Mixed with warning "unable to make hessian positive definite" in Statistical Procedures

Proc Mixed with warning "unable to make hessian positive definite"

SAS_solution — Sun, 25 Mar 2018 19:10:02 GMT

ods output LSMeans=LSM;

PROC MIXED data=adpro3 noclprint;

CLASS trtn monthn usubjid;

MODEL aval = base trtn monthn trtn*monthn /ddfm=kr s;

repeated monthn / subject = usubjid type = un;

lsmeans trtn*monthn / slice= monthn pdiff cl;

RUN;

But in the log the following warning information appeared:

unable to make hessian positive definite.

What's wrong with my coding? What is repeated measure analysis?

Please help. Thank you!

PaigeMiller — Sun, 25 Mar 2018 19:53:53 GMT

SAS_solution — Sun, 25 Mar 2018 20:48:49 GMT

Thank you for the detailed explanation! It is so clear, logic and helpful! Thank you!