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Diffstat (limited to 'example/Persistent_cohomology/custom_persistence_sort.cpp')
| -rw-r--r-- | example/Persistent_cohomology/custom_persistence_sort.cpp | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/example/Persistent_cohomology/custom_persistence_sort.cpp b/example/Persistent_cohomology/custom_persistence_sort.cpp new file mode 100644 index 00000000..9af38611 --- /dev/null +++ b/example/Persistent_cohomology/custom_persistence_sort.cpp @@ -0,0 +1,116 @@ +/* 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): Vincent Rouvreau + * + * Copyright (C) 2014 INRIA Saclay (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/>. + */ + +#include <CGAL/Epick_d.h> +#include <CGAL/point_generators_d.h> +#include <CGAL/algorithm.h> +#include <CGAL/assertions.h> + +#include <gudhi/Alpha_complex.h> +#include <gudhi/Persistent_cohomology.h> + +#include <iostream> +#include <iterator> +#include <vector> +#include <fstream> // for std::ofstream +#include <algorithm> // for std::sort + + +using Kernel = CGAL::Epick_d< CGAL::Dimension_tag<3> >; +using Point = Kernel::Point_d; +using Alpha_complex = Gudhi::alpha_complex::Alpha_complex<Kernel>; + +std::vector<Point> random_points() { + // Instanciate a random point generator + CGAL::Random rng(0); + + // Generate "points_number" random points in a vector + std::vector<Point> points; + + // Generates 1000 random 3D points on a sphere of radius 4.0 + CGAL::Random_points_on_sphere_d<Point> rand_outside(3, 4.0, rng); + CGAL::cpp11::copy_n(rand_outside, 1000, std::back_inserter(points)); + // Generates 2000 random 3D points in a sphere of radius 3.0 + CGAL::Random_points_in_ball_d<Point> rand_inside(3, 3.0, rng); + CGAL::cpp11::copy_n(rand_inside, 2000, std::back_inserter(points)); + + return points; +} + +/* + * Compare two intervals by dimension, then by length. + */ +struct cmp_intervals_by_dim_then_length { + explicit cmp_intervals_by_dim_then_length(Alpha_complex * sc) + : sc_(sc) { } + + template<typename Persistent_interval> + bool operator()(const Persistent_interval & p1, const Persistent_interval & p2) { + if (sc_->dimension(get < 0 > (p1)) == sc_->dimension(get < 0 > (p2))) + return (sc_->filtration(get < 1 > (p1)) - sc_->filtration(get < 0 > (p1)) + > sc_->filtration(get < 1 > (p2)) - sc_->filtration(get < 0 > (p2))); + else + return (sc_->dimension(get < 0 > (p1)) > sc_->dimension(get < 0 > (p2))); + } + Alpha_complex* sc_; +}; + +int main(int argc, char **argv) { + std::vector<Point> points = random_points(); + + // Alpha complex persistence computation from generated points + Alpha_complex alpha_complex_from_points(points, 0.6); + + using Persistent_cohomology = Gudhi::persistent_cohomology::Persistent_cohomology< Alpha_complex, + Gudhi::persistent_cohomology::Field_Zp >; + Persistent_cohomology pcoh(alpha_complex_from_points); + + // initializes the coefficient field for homology - Z/3Z + pcoh.init_coefficients(3); + pcoh.compute_persistent_cohomology(0.2); + + // Custom sort and output persistence + cmp_intervals_by_dim_then_length cmp(&alpha_complex_from_points); + auto persistent_pairs = pcoh.get_persistent_pairs(); + std::sort(std::begin(persistent_pairs), std::end(persistent_pairs), cmp); + for (auto pair : persistent_pairs) { + std::cout << alpha_complex_from_points.dimension(get<0>(pair)) << " " + << alpha_complex_from_points.filtration(get<0>(pair)) << " " + << alpha_complex_from_points.filtration(get<1>(pair)) << std::endl; + } + + // Persistent Betti numbers + std::cout << "The persistent Betti numbers in interval [0.40, 0.41] are : "; + for (int dim = 0; dim < alpha_complex_from_points.dimension(); dim++) + std::cout << "b" << dim << " = " << pcoh.persistent_betti_number(dim, 0.40, 0.41) << " ; "; + std::cout << std::endl; + + // Betti numbers + std::vector<int> betti_numbers = pcoh.betti_numbers(); + std::cout << "The Betti numbers are : "; + for (std::size_t i = 0; i < betti_numbers.size(); i++) + std::cout << "b" << i << " = " << betti_numbers[i] << " ; "; + std::cout << std::endl; + + return 0; +} + |