mahalanobis.hh

// Copyright (C) 2009 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation, version 2 of the License.
//
// Olena is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_FUN_STAT_MAHALANOBIS_HH
# define MLN_FUN_STAT_MAHALANOBIS_HH


# include <cmath>
# include <mln/core/concept/function.hh>
# include <mln/algebra/vec.hh>
# include <mln/algebra/mat.hh>


namespace mln
{

  namespace fun
  {

    namespace stat
    {

      template <typename V>
      struct mahalanobis
        : public Function_v2v< mahalanobis<V> >,
          private metal::equal< V, algebra::vec<V::dim,float> >::check_t
      {
        enum { n = V::dim };
        typedef float result;

        mahalanobis(const algebra::mat<n,n,float>& var,
                    const algebra::vec<n,float>&   mean);
        // Tech. note: using n (instead of V::dim) above helps g++-2.95.

        float operator()(const V& v) const;

        typedef algebra::vec<n,float> mean_t;

        mean_t mean() const;

      protected:
        algebra::mat<n,n,float> var_1_;
        algebra::vec<n,float>   mean_;
      };


# ifndef MLN_INCLUDE_ONLY

      template <typename V>
      inline
      mahalanobis<V>::mahalanobis(const algebra::mat<n,n,float>& var,
                                  const algebra::vec<n,float>&   mean)
      {
        var_1_ = var._1();
        mean_  = mean;
      }

      template <typename V>
      inline
      float
      mahalanobis<V>::operator()(const V& v) const
      {
        return std::sqrt((v - mean_).t() * var_1_ * (v - mean_));
      }

      template <typename V>
      inline
      typename mahalanobis<V>::mean_t
      mahalanobis<V>::mean() const
      {
        return mean_;
      }

# endif // ! MLN_INCLUDE_ONLY

    } // end of namespace mln::fun::stat

  } // end of namespace mln::fun

} // end of namespace mln


#endif // ! MLN_FUN_STAT_MAHALANOBIS_HH