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function marginal = marginal_nodes(engine, query, add_ev)
% MARGINAL_NODES Compute the marginal on the specified query nodes (cond_gauss)
% marginal = marginal_nodes(engine, query, add_ev)
%
% 'query' must be a singleton set
% add_ev is an optional argument; if 1, we will "inflate" the marginal of observed nodes
% to their original size, adding 0s to the positions which contradict the evidence
if nargin < 3, add_ev = 0; end
if length(query) ~= 1
error('cond_gauss_inf_engine can only handle marginal queries on single nodes')
end
j = query;
bnet = bnet_from_engine(engine);
if myismember(j, bnet.cnodes)
if ~myismember(j, engine.onodes)
[m, C] = collapse_mog(engine.mu{j}, engine.Sigma{j}, engine.T);
marginal.mu = m;
marginal.Sigma = C;
marginal.T = 1.0; % single mixture component
else
marginal.mu = engine.evidence{j};
k = bnet.node_sizes(j);
marginal.Sigma = zeros(k,k);
marginal.T = 1.0; % since P(E|E)=1
end
else
marginal = pot_to_marginal(marginalize_pot(engine.joint_dmarginal, j));
if add_ev
marginal = add_ev_to_dmarginal(marginal, engine.evidence, bnet.node_sizes);
end
end
marginal.domain = query;
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