Effect of FOCE vs FOCE INTER on success of covariance step within a model with additive error

From: "Doshi, Sameer" sdoshi@amgen.com Subject: [NMusers] Effect of FOCE vs FOCE INTER on success of covariance step within a model with additive error Date: Thu, 9 Mar 2006 18:19:10 -0800 Hello, I am trying to fit a model with additive error; Y=EFF+ERR(1) using FOCE which converges successfully but ends with the following error: 0R MATRIX ALGORITHMICALLY NON-POSITIVE-SEMIDEFINITE BUT NONSINGULAR 0COVARIANCE STEP ABORTED I tried running the same model with FOCE INTER without making any other changes to the control stream. When running the model with FOCE INTER, the model converged (with the same results and objective function) and with a successful covariance step. Could the group please offer some insight as to why using FOCE INTER resulted in a successful covarariance step when FOCE did not? Thanks for your help, Sameer Sameer Doshi Pharmacokinetics and Drug Metabolism, Amgen Inc. (805) 447-6941