hessianReg is a function to compute the Hessian matrix estimate of non-zero regularized estimators. Implemented only for zipath object with family="negbin" in the current version.
References
Zhu Wang, Shuangge Ma and Ching-Yun Wang (2015) Variable selection for zero-inflated and overdispersed data with application to health care demand in Germany, Biometrical Journal. 57(5):867-84.