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Diffstat (limited to 'src/Persistence_representations/include/gudhi/Persistence_landscape_on_grid_exact.h')
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1 files changed, 107 insertions, 0 deletions
diff --git a/src/Persistence_representations/include/gudhi/Persistence_landscape_on_grid_exact.h b/src/Persistence_representations/include/gudhi/Persistence_landscape_on_grid_exact.h new file mode 100644 index 00000000..25f71e27 --- /dev/null +++ b/src/Persistence_representations/include/gudhi/Persistence_landscape_on_grid_exact.h @@ -0,0 +1,107 @@ +/* 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): Mathieu Carriere + * + * Copyright (C) 2018 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 LANDSCAPE_H_ +#define LANDSCAPE_H_ + +// gudhi include +#include <gudhi/read_persistence_from_file.h> +#include <gudhi/common_persistence_representations.h> +#include <gudhi/Debug_utils.h> + +// standard include +#include <cmath> +#include <iostream> +#include <vector> +#include <limits> +#include <fstream> +#include <sstream> +#include <algorithm> +#include <string> +#include <utility> +#include <functional> + +namespace Gudhi { +namespace Persistence_representations { + +/** + * \class Persistence_landscape_on_grid_exact gudhi/Persistence_landscape_on_grid_exact.h + * \brief A class implementing exact persistence landscapes by approximating them on a collection of grid points + * + * \ingroup Persistence_representations + * + * \details + * In this class, we propose a way to approximate landscapes by sampling the x-axis of the persistence diagram and evaluating the (exact) landscape functions on the sample projections onto the diagonal. Note that this is a different approximation scheme + * from the one proposed in Persistence_landscape_on_grid, which puts a grid on the diagonal, maps the persistence intervals on this grid and computes the (approximate) landscape functions on the samples. + * Hence, the difference is that we do not modify the diagram in this implementation, but the code can be slower to run. +**/ + +class Persistence_landscape_on_grid_exact { + + protected: + Persistence_diagram diagram; + int res_x, nb_ls; + double min_x, max_x; + + public: + + /** \brief Persistence_landscape_on_grid_exact constructor. + * \ingroup Persistence_landscape_on_grid_exact + * + * @param[in] _diagram persistence diagram. + * @param[in] _nb_ls number of landscape functions. + * @param[in] _min_x minimum value of samples. + * @param[in] _max_x maximum value of samples. + * @param[in] _res_x number of samples. + * + */ + Persistence_landscape_on_grid_exact(const Persistence_diagram & _diagram, int _nb_ls = 5, double _min_x = 0.0, double _max_x = 1.0, int _res_x = 10){diagram = _diagram; nb_ls = _nb_ls; min_x = _min_x; max_x = _max_x; res_x = _res_x;} + + /** \brief Computes the landscape approximation of a diagram. + * \ingroup Persistence_landscape_on_grid_exact + * + */ + std::vector<std::vector<double> > vectorize() const { + std::vector<std::vector<double> > ls; for(int i = 0; i < nb_ls; i++) ls.emplace_back(); + int num_pts = diagram.size(); double step = (max_x - min_x)/res_x; + + for(int i = 0; i < res_x; i++){ + double x = min_x + i*step; double t = x / std::sqrt(2); std::vector<double> events; + for(int j = 0; j < num_pts; j++){ + double px = diagram[j].first; double py = diagram[j].second; + if(t >= px && t <= py){ if(t >= (px+py)/2) events.push_back(std::sqrt(2)*(py-t)); else events.push_back(std::sqrt(2)*(t-px)); } + } + + std::sort(events.begin(), events.end(), [](const double & a, const double & b){return a > b;}); int nb_events = events.size(); + for (int j = 0; j < nb_ls; j++){ if(j < nb_events) ls[j].push_back(events[j]); else ls[j].push_back(0); } + } + return ls; + } + + + + +}; // class Persistence_landscape_on_grid_exact +} // namespace Persistence_representations +} // namespace Gudhi + +#endif // LANDSCAPE_H_ |