topic Re: PROC COUNTREG, WARNING: The Hessian matrix is singular. in Statistical Procedures https://communities.sas.com/t5/Statistical-Procedures/PROC-COUNTREG-WARNING-The-Hessian-matrix-is-singular/m-p/159695#M8308 <HTML><HEAD></HEAD><BODY><P>It might be that some of your categories (CLASSES) are empty in some data subsets, leaving no effect to estimate (i.e. your model has a isSmoker effect but all females are non-smokers).</P><P></P><P>PG</P></BODY></HTML> Sun, 02 Feb 2014 23:24:40 GMT PGStats 2014-02-02T23:24:40Z PROC COUNTREG, WARNING: The Hessian matrix is singular. https://communities.sas.com/t5/Statistical-Procedures/PROC-COUNTREG-WARNING-The-Hessian-matrix-is-singular/m-p/159694#M8307 <HTML><HEAD></HEAD><BODY><P>Hi everyone,</P><P></P><P>I am wondering if anyone has any insight on my problem. I am running multiple models with the same variables (full sample, male sample, female sample) and on SOME of my models I am getting zeros and the warning: "The Hessian matrix is singular." Now, it is the same data, same variables, but some of the models produce results and some do not. I am not sure whether my machine has gone rogue or if I am violating some assumption...</P><P></P><P>I am running ZINB models. Anyone have any experience with this?</P><P></P><P>Thanks so much,</P><P>Nayika</P></BODY></HTML> Sun, 02 Feb 2014 17:56:00 GMT https://communities.sas.com/t5/Statistical-Procedures/PROC-COUNTREG-WARNING-The-Hessian-matrix-is-singular/m-p/159694#M8307 Nayika 2014-02-02T17:56:00Z Re: PROC COUNTREG, WARNING: The Hessian matrix is singular. https://communities.sas.com/t5/Statistical-Procedures/PROC-COUNTREG-WARNING-The-Hessian-matrix-is-singular/m-p/159695#M8308 <HTML><HEAD></HEAD><BODY><P>It might be that some of your categories (CLASSES) are empty in some data subsets, leaving no effect to estimate (i.e. your model has a isSmoker effect but all females are non-smokers).</P><P></P><P>PG</P></BODY></HTML> Sun, 02 Feb 2014 23:24:40 GMT https://communities.sas.com/t5/Statistical-Procedures/PROC-COUNTREG-WARNING-The-Hessian-matrix-is-singular/m-p/159695#M8308 PGStats 2014-02-02T23:24:40Z