Program Listing for File Isomap.hpp

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#ifndef DIMREDTOOLS_INCLUDE_DIMREDTOOLS_ISOMAP_HPP_
#define DIMREDTOOLS_INCLUDE_DIMREDTOOLS_ISOMAP_HPP_

#include "DimRedTools.hpp"
#include <optional>
#include <unordered_set>

namespace dim_red {

class Isomap {
public:
    Isomap(std::optional<int> n_neighbors = 5, std::optional<double> radius = std::nullopt,
           int n_components = 2, int max_iter = 100, double eps = 1e-4, double learning_rate = 0.2,
           int random_state = 0, const std::string &neighbors_algorithm = "auto",
           const std::string &metric = "euclidean");

    ~Isomap();

    Matrix fitTransform(const Eigen::Ref<const Matrix> &x);

    NearestNeighbors *nbrs_;
    Matrix dist_matrix_;

private:
    using Graph = std::vector<std::unordered_set<int>>;

    Graph buildGraph(Eigen::Ref<const Matrix> x);

    void dijkstra(const Graph &graph, int start, Eigen::Ref<Vector> distances) const;

    void dijkstra(const Graph &graph);

    int connectedComponents(const Graph &graph, Eigen::Ref<IntVector> labels) const;

    void fixConnectedComponents(Eigen::Ref<const Matrix> x, int components,
                                Eigen::Ref<IntVector> labels, Graph *graph) const;

    std::optional<int> n_neighbors_;
    std::optional<double> radius_;
    int n_components_;
    int max_iter_;
    double eps_;
    double learning_rate_;
    int random_state_;
    std::string neighbors_algorithm_;
    std::string metric_;
};

}  // namespace dim_red

#endif  // DIMREDTOOLS_INCLUDE_DIMREDTOOLS_ISOMAP_HPP_