# Hessian Matrix of Regularized Estimators

### Description

Constructing Hessian matrix for regularized regression parameters.

### Usage

1 | ```
hessianReg(x, which, ...)
``` |

### Arguments

`x` |
a fitted model object. |

`which` |
which penalty parameter(s)? |

`...` |
arguments passed to the |

### Details

`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.

### Value

A matrix containing the Hessian matrix estimate for the non-zero parameters.

### Author(s)

Zhu Wang <zwang@connecticutchildrens.org>

### 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.

### See Also

`breadReg`

, `meatReg`

### Examples

1 2 3 |