deviation.hh

// Copyright (C) 2009, 2010 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_ACCU_STAT_DEVIATION_HH
# define MLN_ACCU_STAT_DEVIATION_HH


# include <mln/accu/internal/base.hh>
# include <mln/accu/math/count.hh>
# include <mln/accu/math/sum.hh>
# include <mln/math/sqr.hh>
# include <mln/math/sqrt.hh>


namespace mln
{

  namespace accu
  {

    namespace stat
    {


    template <typename T,
              typename S = mln_sum(T),
              typename M = S>
    struct deviation : public mln::accu::internal::base< M , deviation<T,S,M> >
    {
      typedef T argument;
      typedef M result;

      deviation(const T mean);

      void init();
      void take(const argument& t);
      void take(const deviation<T,S,M>& other);

      M to_result() const;
      operator M () const;

      bool is_valid() const;

    protected:

      accu::math::count<T> count_;

      // NOTE: accu::math::sum takes mln_sum(T) as first template
      // parameter since in the core of the deviation::take method,
      // this accumulator takes data of type mln_sum(T).
      accu::math::sum<mln_sum(T),S>   sum_;
      T mean_;
    };



    template <typename I, typename S, typename M>
    struct deviation< util::pix<I>, S,M >;


    namespace meta
    {

      struct deviation : public Meta_Accumulator< deviation >
      {
        template < typename T,
                   typename S = mln_sum(T),
                   typename M = S >
        struct with
        {
          typedef accu::stat::deviation<T,S,M> ret;
        };
      };

    } // end of namespace mln::accu::meta


# ifndef MLN_INCLUDE_ONLY

    template <typename T, typename S, typename M>
    inline
    deviation<T,S,M>::deviation(const T mean)
    {
      init();
      mean_ = mean;
    }

    template <typename T, typename S, typename M>
    inline
    void
    deviation<T,S,M>::init()
    {
      count_.init();
      sum_.init();
    }

    template <typename T, typename S, typename M>
    inline
    void deviation<T,S,M>::take(const argument& t)
    {
      count_.take(t);
      sum_.take(mln::math::sqr(t - mean_));
    }

    template <typename T, typename S, typename M>
    inline
    void
    deviation<T,S,M>::take(const deviation<T,S,M>& other)
    {
      // FIXME
      count_.take(other.count_);
      sum_.take(other.sum_);
    }

    template <typename T, typename S, typename M>
    inline
    M
    deviation<T,S,M>::to_result() const
    {
      unsigned n = count_.to_result();
      if (n == 0u)
        return M(); // Safety.
      return static_cast<M>(mln::math::sqrt(sum_.to_result() / n));
    }

    template <typename T, typename S, typename M>
    inline
    deviation<T,S,M>::operator M() const
    {
      return to_result();
    }

    template <typename T, typename S, typename M>
    inline
    bool
    deviation<T,S,M>::is_valid() const
    {
      return count_.to_result() != 0;
    }

# endif // ! MLN_INCLUDE_ONLY

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

  } // end of namespace mln::accu

} // end of namespace mln


#endif // ! MLN_ACCU_STAT_DEVIATION_HH