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/base/Vector.h>
#include <gtsam/discrete/DiscreteBayesTree.h>
#include <gtsam/discrete/DiscreteFactorGraph.h>
 
namespace gtsam {
 
class DiscreteMarginals {
 protected:
  DiscreteBayesTree::shared_ptr bayesTree_;
 
 public:
  DiscreteMarginals() {}
 
  DiscreteMarginals(const DiscreteFactorGraph& graph) {
    bayesTree_ = graph.eliminateMultifrontal();
  }
 
  DiscreteFactor::shared_ptr operator()(Key variable) const {
    // Compute marginal
    DiscreteFactor::shared_ptr marginalFactor =
        bayesTree_->marginalFactor(variable, &EliminateDiscrete);
    return marginalFactor;
  }
 
  Vector marginalProbabilities(const DiscreteKey& key) const {
    // Compute marginal
    DiscreteFactor::shared_ptr marginalFactor = this->operator()(key.first);
 
    // Create result
    Vector vResult(key.second);
    for (size_t state = 0; state < key.second; ++state) {
      DiscreteValues values;
      values[key.first] = state;
      vResult(state) = (*marginalFactor)(values);
    }
    return vResult;
  }
};
 
} /* namespace gtsam */