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<html>
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<title>
Netlab Reference Manual nethess
</title>
</head>
<body>
<H1> nethess
</H1>
<h2>
Purpose
</h2>
Evaluate network Hessian
<p><h2>
Synopsis
</h2>
<PRE>
h = neterr(w, net, x, t)
[h, varargout] = neterr(w, net, x, t, varargin)
</PRE>
<p><h2>
Description
</h2>
<p><CODE>h = nethess(w, net, x, t)</CODE> takes a weight vector <CODE>w</CODE> and a network
data structure <CODE>net</CODE>, together with the matrix <CODE>x</CODE> of input
vectors and the matrix <CODE>t</CODE> of target vectors, and returns the
value of the Hessian evaluated at <CODE>w</CODE>.
<p><CODE>[e, varargout] = nethess(w, net, x, t, varargin)</CODE> also returns any additional
return values from the network Hessian function, and passes additional arguments
to that function.
<p><h2>
Example
</h2>
<p>In <CODE>evidence</CODE>, this function is called once to compute the
data contribution to the Hessian
<PRE>
[h, dh] = nethess(w, net, x, t, dh);
</PRE>
and again to update the Hessian for new values of the hyper-parameters
<PRE>
h = nethess(w, net, x, t, dh);
</PRE>
<p><h2>
See Also
</h2>
<CODE><a href="neterr.htm">neterr</a></CODE>, <CODE><a href="netgrad.htm">netgrad</a></CODE>, <CODE><a href="netopt.htm">netopt</a></CODE><hr>
<b>Pages:</b>
<a href="index.htm">Index</a>
<hr>
<p>Copyright (c) Ian T Nabney (1996-9)
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