Hello all,

I’ve been trying to extend this 2014 JEDC by Fabio Milani

https://econpapers.repec.org/article/eeedyncon/v_3a47_3ay_3a2014_3ai_3ac_3ap_3a94-114.htm

Which estimates a linear NK model with learning. I’ve tried to code the likelihood function as I interpret it and when maximizing using Matlab’s Fminunc routine gives me a Hessian whose inverse is not semi-positive definite, and therefore cannot be used for the proposal density in a Metropolis Hastings algorithm.

Have any others encountered a similar problem? I thought perhaps I could use the nearest Semi-positive definite matrix to the inverse hessian for the proposal density?