comparison toolboxes/FullBNT-1.0.7/netlab3.3/gmmpost.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [post, a] = gmmpost(mix, x)
+%GMMPOST Computes the class posterior probabilities of a Gaussian mixture model.
+%
+%	Description
+%	This function computes the posteriors POST (i.e. the probability of
+%	each component conditioned on the data P(J|X)) for a Gaussian mixture
+%	model.   The data structure MIX defines the mixture model, while the
+%	matrix X contains the data vectors.  Each row of X represents a
+%	single vector.
+%
+%	See also
+%	GMM, GMMACTIV, GMMPROB
+%
+
+%	Copyright (c) Ian T Nabney (1996-2001)
+
+% Check that inputs are consistent
+errstring = consist(mix, 'gmm', x);
+if ~isempty(errstring)
+  error(errstring);
+end
+
+ndata = size(x, 1);
+
+a = gmmactiv(mix, x);
+
+post = (ones(ndata, 1)*mix.priors).*a;
+s = sum(post, 2);
+if any(s==0)
+   warning('Some zero posterior probabilities')
+   % Set any zeros to one before dividing
+   zero_rows = find(s==0);
+   s = s + (s==0);
+   post(zero_rows, :) = 1/mix.ncentres;
+end
+post = post./(s*ones(1, mix.ncentres));