x</CODE> of input values, and a matrix <CODE>t</CODE> of 
target values, together with the contribution <CODE>hdata</CODE> arising from
the data dependent term in the Hessian, and returns the full Hessian
matrix <CODE>h</CODE> corresponding to the second derivatives of the negative
log posterior distribution. This version saves computation time if
<CODE>hdata</CODE> has already been evaluated for the current weight and bias
values.

<p><h2>
Example
</h2>
For the standard regression framework with a Gaussian