From 361abfcfa9ec18c76837f847f8e2e3a060cf7db7 Mon Sep 17 00:00:00 2001 From: MathieuCarriere Date: Thu, 19 Mar 2020 17:02:55 -0400 Subject: added decoding function --- src/Simplex_tree/include/gudhi/Simplex_tree.h | 82 +++++++++++---------------- 1 file changed, 34 insertions(+), 48 deletions(-) (limited to 'src/Simplex_tree') diff --git a/src/Simplex_tree/include/gudhi/Simplex_tree.h b/src/Simplex_tree/include/gudhi/Simplex_tree.h index 50b8e582..9008c5f2 100644 --- a/src/Simplex_tree/include/gudhi/Simplex_tree.h +++ b/src/Simplex_tree/include/gudhi/Simplex_tree.h @@ -87,6 +87,8 @@ class Simplex_tree { /* \brief Set of nodes sharing a same parent in the simplex tree. */ typedef Simplex_tree_siblings Siblings; + enum Extended_simplex_type {UP, DOWN, EXTRA}; + struct Key_simplex_base_real { Key_simplex_base_real() : key_(-1) {} void assign_key(Simplex_key k) { key_ = k; } @@ -1486,66 +1488,50 @@ class Simplex_tree { } } - /** \brief Retrieve good values for extended persistence, and separate the - * diagrams into the ordinary, relative, extended+ and extended- subdiagrams. + /** \brief Retrieve the original filtration value for a given simplex in the Simplex_tree. Since the + * computation of extended persistence requires modifying the filtration values, this function can be used + * to recover the original values. Moreover, computing extended persistence requires adding new simplices + * in the Simplex_tree. Hence, this function also outputs the type of each simplex. It can be either UP (which means + * that the simplex was present originally, and is thus part of the ascending extended filtration), DOWN (which means + * that the simplex is the cone of an original simplex, and is thus part of the descending extended filtration) or + * EXTRA (which means the simplex is the cone point). Note that if the simplex type is DOWN, the original filtration value + * is set to be the original filtration value of the corresponding (not coned) original simplex. * \pre This function should be called only if `extend_filtration()` has been called first! - * \post The coordinates of the persistence diagram points might be a little different than the - * original filtration values due to the internal transformation (scaling to [-2,-1]) that is - * performed on these values during the computation of extended persistence. - * @param[in] dgm Persistence diagram obtained after calling `extend_filtration()`, - * `initialize_filtration()`, and `Gudhi::persistent_cohomology::Persistent_cohomology< FilteredComplex, CoefficientField >::compute_persistent_cohomology()`. - * @param[in] efd Structure containing the minimum and maximum values of the original filtration - * @return A vector of four persistence diagrams. The first one is Ordinary, the - * second one is Relative, the third one is Extended+ and the fourth one is Extended-. - * See section 2.2 in https://link.springer.com/article/10.1007/s10208-017-9370-z for a description of these subtypes. + * \post The output filtration value is supposed to be the same, but might be a little different, than the + * original filtration value, due to the internal transformation (scaling to [-2,-1]) that is + * performed on the original filtration values during the computation of extended persistence. + * @param[in] f Filtration value of the simplex in the extended (i.e., modified) filtration. + * @param[in] efd Structure containing the minimum and maximum values of the original filtration. This the output of `extend_filtration()`. + * @return A pair containing the original filtration value of the simplex as well as the simplex type. */ - std::vector>>> extended_persistence_subdiagrams(const std::vector>>& dgm, const Extended_filtration_data& efd){ - std::vector>>> new_dgm(4); - Filtration_value x, y; + std::pair decode_extended_filtration(Filtration_value f, const Extended_filtration_data& efd){ + std::pair p; Filtration_value minval = efd.minval; Filtration_value maxval = efd.maxval; - for(unsigned int i = 0; i < dgm.size(); i++){ - int h = dgm[i].first; - Filtration_value px = dgm[i].second.first; - Filtration_value py = dgm[i].second.second; - if(std::isinf(py)) continue; - else{ - if ((px <= -1) & (py <= -1)){ - x = minval + (maxval-minval)*(px + 2); - y = minval + (maxval-minval)*(py + 2); - new_dgm[0].push_back(std::make_pair(h, std::make_pair(x,y))); - } - else if ((px >= 1) & (py >= 1)){ - x = minval - (maxval-minval)*(px - 2); - y = minval - (maxval-minval)*(py - 2); - new_dgm[1].push_back(std::make_pair(h, std::make_pair(x,y))); - } - else { - x = minval + (maxval-minval)*(px + 2); - y = minval - (maxval-minval)*(py - 2); - if (x <= y){ - new_dgm[2].push_back(std::make_pair(h, std::make_pair(x,y))); - } - else{ - new_dgm[3].push_back(std::make_pair(h, std::make_pair(x,y))); - } - } - } + if (f >= -2 && f <= -1){ + p.first = minval + (maxval-minval)*(f + 2); p.second = UP; } - return new_dgm; - } + else if (f >= 1 && f <= 2){ + p.first = minval - (maxval-minval)*(f - 2); p.second = DOWN; + } + else{ + p.first = -3; p.second = EXTRA; + } + return p; + }; /** \brief Extend filtration for computing extended persistence. * This function only uses the filtration values at the 0-dimensional simplices, * and computes the extended persistence diagram induced by the lower-star filtration * computed with these values. * \post Note that after calling this function, the filtration - * values are actually modified. The function `extended_persistence_subdiagrams()` - * retrieves the original values and separates the extended persistence diagram points - * w.r.t. their types (Ord, Rel, Ext+, Ext-) and should always be called after - * computing the persistent homology of the extended simplicial complex. + * values are actually modified. The function `decode_extended_filtration()` + * retrieves the original values and outputs the extended simplex type. * \pre Note that this code creates an extra vertex internally, so you should make sure that - * the Simplex tree does not contain a vertex with the largest Vertex_handle. + * the Simplex tree does not contain a vertex with the largest Vertex_handle. + * @return A data structure containing the maximum and minimum values of the original filtration. + * It is meant to be provided as input to `decode_extended_filtration()` in order to retrieve + * the original filtration values for each simplex. */ Extended_filtration_data extend_filtration() { -- cgit v1.2.3