DiscreteMarginals.h

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/* ----------------------------------------------------------------------------

 * GTSAM Copyright 2010, Georgia Tech Research Corporation,
 * Atlanta, Georgia 30332-0415
 * All Rights Reserved
 * Authors: Frank Dellaert, et al. (see THANKS for the full author list)

 * See LICENSE for the license information

 * -------------------------------------------------------------------------- */

#pragma once

#include <gtsam/discrete/DiscreteFactorGraph.h>
#include <gtsam/discrete/DiscreteBayesTree.h>
#include <gtsam/base/Vector.h>

namespace gtsam {

  class DiscreteMarginals {

  protected:

    DiscreteBayesTree::shared_ptr bayesTree_;

  public:

  DiscreteMarginals(const DiscreteFactorGraph& graph) {
    bayesTree_ = graph.eliminateMultifrontal();
  }

  DiscreteFactor::shared_ptr operator()(Key variable) const {
    // Compute marginal
    DiscreteFactor::shared_ptr marginalFactor;
    marginalFactor = bayesTree_->marginalFactor(variable, &EliminateDiscrete);
    return marginalFactor;
  }

  Vector marginalProbabilities(const DiscreteKey& key) const {
    // Compute marginal
    DiscreteFactor::shared_ptr marginalFactor;
    marginalFactor = bayesTree_->marginalFactor(key.first, &EliminateDiscrete);

    //Create result
    Vector vResult(key.second);
    for (size_t state = 0; state < key.second ; ++ state) {
      DiscreteFactor::Values values;
      values[key.first] = state;
      vResult(state) = (*marginalFactor)(values);
    }
    return vResult;
  }

  };

} /* namespace gtsam */