📄 gtmem.htm
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<html><head><title>Netlab Reference Manual gtmem</title></head><body><H1> gtmem</H1><h2>Purpose</h2>EM algorithm for Generative Topographic Mapping.<p><h2>Synopsis</h2><PRE>[net, options, errlog] = gtmem(net, t, options)</PRE><p><h2>Description</h2><CODE>[net, options, errlog] = gtmem(net, t, options)</CODE> uses the ExpectationMaximization algorithm to estimate the parameters ofa GTM defined by a data structure <CODE>net</CODE>.The matrix <CODE>t</CODE> represents the data whose expectationis maximized, with each row corresponding to a vector. It is assumedthat the latent data <CODE>net.X</CODE> has been set following a call to<CODE>gtminit</CODE>, for example. The optional parameters have the following interpretations.<p><CODE>options(1)</CODE> is set to 1 to display error values; also logs error values in the return argument <CODE>errlog</CODE>.If <CODE>options(1)</CODE> is set to 0,then only warning messages are displayed. If <CODE>options(1)</CODE> is -1,then nothing is displayed.<p><CODE>options(3)</CODE> is a measure of the absolute precision required of the errorfunction at the solution. If the change in log likelihood between two steps ofthe EM algorithm is less than this value, then the function terminates.<p><CODE>options(14)</CODE> is the maximum number of iterations; default 100.<p>The optional return value <CODE>options</CODE> contains the final error value (i.e. data log likelihood) in<CODE>options(8)</CODE>. <p><h2>Examples</h2>The following code fragment sets up a GTM, initialisesthe latent data sample and RBFparameters from the data, sets the options and trains the model.<PRE>% Create and initialise GTM modelnet = gtm(latentdim, nlatent, datadim, numrbfcentres, ... 'gaussian', 0.1);<p>options = foptions;options(1) = -1;options(7) = 1; % Set width factor of RBFnet = gtminit(net, options, data, 'regular', latentshape, [4 4]);<p>options = foptions;options(14) = 30;options(1) = 1;[net, options] = gtmem(net, data, options);</PRE><p><h2>See Also</h2><CODE><a href="gtm.htm">gtm</a></CODE>, <CODE><a href="gtminit.htm">gtminit</a></CODE><hr><b>Pages:</b><a href="index.htm">Index</a><hr><p>Copyright (c) Ian T Nabney (1996-9)</body></html>⌨️ 快捷键说明
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