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/* This file is part of the Gudhi Library. The Gudhi library
* (Geometric Understanding in Higher Dimensions) is a generic C++
* library for computational topology.
*
* Author(s): Pawel Dlotko
*
* Copyright (C) 2015 INRIA (France)
*
* This program 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, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef HAUSDORFF_DISTANCES_H
#define HAUSDORFF_DISTANCES_H
#include <cmath>
#include <limits>
#include <vector>
#include <cstdlib>
#include <iostream>
/**
* This file contains various implementations of Hausrodff distances between collections of points. It contains various implementations that can be used for specific case.
**/
/**
* The implementation below works for a case of a metric space given by a distance matrix, and a subspace of a metric space. Our task is to find a Hausdorff distance between the subspace and the whole space.
* The input is a distance matrix (lower triangular part) and a vector of bools indicating a subspace (elementss set to true belongs to the space, the elements set to false do not).
**/
class Hausdorff_distance_between_subspace_and_the_whole_metric_space
{
public:
Hausdorff_distance_between_subspace_and_the_whole_metric_space( const std::vector< std::vector<double> >& distance_matrix ):distance_matrix(distance_matrix){}
double operator()( const std::vector< bool >& is_subspace )
{
double maximal_distance = -std::numeric_limits<double>::max();
for ( size_t j = 0 ; j != this->distance_matrix.size() ; ++j )
{
double minimal_distance = std::numeric_limits<double>::max();
for ( size_t i = 0 ; i != this->distance_matrix.size() ; ++i )
{
if ( !is_subspace[i] )continue;
double distance = 0;
if ( i < j )
{
distance = this->distance_matrix[i][j];
}
else
{
if ( i > j )distance = this->distance_matrix[j][i];
}
if ( distance > minimal_distance )minimal_distance = distance;
}
if ( maximal_distance < minimal_distance )maximal_distance = minimal_distance;
}
return maximal_distance;
}//Hausdorff_distance_between_subspace_and_the_whole_metric_space
double operator()( const std::vector< size_t >& subspace , const std::vector< size_t >& space = std::vector< size_t >() )
{
bool dbg = false;
if ( dbg )
{
std::cerr << "Calling double operator()( const std::vector< size_t >& subspace , const std::vector< size_t >& space = std::vector< size_t >() ) method \n";
std::cerr << "subspace.size() : " << subspace.size() << std::endl;
}
double maximal_distance = -std::numeric_limits<double>::max();
for ( size_t j = 0 ; j != this->distance_matrix.size() ; ++j )
{
double minimal_distance = std::numeric_limits<double>::max();
for ( size_t i = 0 ; i != subspace.size() ; ++i )
{
double distance = 0;
if ( subspace[i] < j )
{
distance = this->distance_matrix[ j ][ subspace[i] ];
}
else
{
if ( subspace[i] > j )distance = this->distance_matrix[ subspace[i] ][ j ];
}
if ( distance < minimal_distance )minimal_distance = distance;
}
if ( maximal_distance < minimal_distance )maximal_distance = minimal_distance;
}
if ( dbg )
{
std::cerr << "maximal_distance : " << maximal_distance << std::endl;
getchar();
}
return maximal_distance;
}//Hausdorff_distance_between_subspace_and_the_whole_metric_space
private:
const std::vector< std::vector<double> >& distance_matrix;
};
template <typename PointType , typename distanceFunction >
std::vector< std::vector<double> > compute_all_to_all_distance_matrix_between_points( const std::vector< PointType >& points )
{
bool dbg = false;
std::vector< std::vector<double> > result;
result.reserve( points.size() );
distanceFunction f;
for ( size_t i = 0 ; i != points.size() ; ++i )
{
std::vector<double> this_row;
this_row.reserve( i );
for ( size_t j = 0 ; j != i ; ++j )
{
double distance = f( points[i] , points[j] );
if ( dbg ){std::cerr << "The distance between point : " << i << " and the point : " << j << " is :" << distance << std::endl;}
this_row.push_back( distance );
}
result.push_back( this_row );
}
return result;
}//compute_all_to_all_distance_matrix_between_points
template <typename T>
class identity
{
public:
T& operator()( T& org )
{
return org;
}
};
#endif
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