# nethess

## Purpose

Evaluate network Hessian

## Synopsis

    h = neterr(w, net, x, t)
    [h, varargout] = neterr(w, net, x, t, varargin)

## Description

`h = nethess(w, net, x, t)` takes a weight vector `w` and a network data structure `net`, together with the matrix `x` of input vectors and the matrix `t` of target vectors, and returns the value of the Hessian evaluated at `w`.

`[e, varargout] = nethess(w, net, x, t, varargin)` also returns any additional return values from the network Hessian function, and passes additional arguments to that function.

## Example

In `evidence`, this function is called once to compute the data contribution to the Hessian

    [h, dh] = nethess(w, net, x, t, dh);

and again to update the Hessian for new values of the hyper-parameters

    h = nethess(w, net, x, t, dh);

## See Also

`neterr`, `netgrad`, `netopt`

Pages: Index

Copyright (c) Ian T Nabney (1996-9)