Hi, I am trying to generate correlation matrix of different structure (Compound Symmetry, AR1, TOEPLITZ, Unstructured, Banded etc). My generated Compound Symmetry and AR1 matrix are coming positive definite so I can consider them as Correlation matrix. However, when I generate Unstructured, Toeplitz, Compound symmetry with band 2, AR1 with band2, I cannot ensure positive definiteness in those matrices, so I cannot consider them as correlation matrix. I need your suggestion to generate positive definite correlation matrices under the Unstructured, Toeplitz, Compound symmetry with band 2, AR1 with band2 structure. Kindly refer relevant article if you are aware of. Thanks & Regards MGK --------------Madan Gopal Kundu PhD Scholar Indiana University Purdue University Indianapolis (IUPUI) Indianapolis, Indiana 46202, USA Your Mail works best with the New Yahoo Optimized IE8. Get it NOW! http://downloads.yahoo.com/in/internetexplorer/ You may leave the list at any time by sending the command SIGNOFF allstat to [log in to unmask], leaving the subject line blank.