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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));
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