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Diffstat (limited to 'src/Coxeter_triangulation/include/gudhi/Functions/Linear_transformation.h')
-rw-r--r-- | src/Coxeter_triangulation/include/gudhi/Functions/Linear_transformation.h | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/src/Coxeter_triangulation/include/gudhi/Functions/Linear_transformation.h b/src/Coxeter_triangulation/include/gudhi/Functions/Linear_transformation.h new file mode 100644 index 00000000..4cb5ca84 --- /dev/null +++ b/src/Coxeter_triangulation/include/gudhi/Functions/Linear_transformation.h @@ -0,0 +1,96 @@ +/* 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): Siargey Kachanovich + * + * Copyright (C) 2019 Inria + * + * Modification(s): + * - YYYY/MM Author: Description of the modification + */ + +#ifndef FUNCTIONS_LINEAR_TRANSFORMATION_H_ +#define FUNCTIONS_LINEAR_TRANSFORMATION_H_ + +#include <cstdlib> + +#include <gudhi/Functions/Function.h> +#include <Eigen/Dense> + +namespace Gudhi { + +namespace coxeter_triangulation { + +/** \class Linear_transformation + * \brief Transforms the zero-set of the function by a given linear transformation. + * The underlying function corresponds to f(M*x), where M is the transformation matrix. + * + * \tparam Function_ The function template parameter. Should be a model of + * the concept FunctionForImplicitManifold. + * + * \ingroup coxeter_triangulation + */ +template <class Function_> +struct Linear_transformation : public Function { + + /** + * \brief Value of the function at a specified point. + * @param[in] p The input point. The dimension needs to coincide with the ambient dimension. + */ + Eigen::VectorXd operator()(const Eigen::VectorXd& p) const { + Eigen::VectorXd result = fun_(matrix_.householderQr().solve(p)); + return result; + } + + /** \brief Returns the domain (ambient) dimension. */ + std::size_t amb_d() const {return fun_.amb_d();} + + /** \brief Returns the codomain dimension. */ + std::size_t cod_d() const {return fun_.cod_d();} + + /** \brief Returns a point on the zero-set. */ + Eigen::VectorXd seed() const { + Eigen::VectorXd result = fun_.seed(); + result = matrix_ * result; + return result; + } + + /** + * \brief Constructor of a linearly transformed function. + * + * @param[in] function The function to be linearly transformed. + * @param[in] matrix The transformation matrix. Its dimension should be d*d, + * where d is the domain (ambient) dimension of 'function'. + */ + Linear_transformation(const Function_& function, const Eigen::MatrixXd& matrix) : + fun_(function), matrix_(matrix) { + } + +private: + Function_ fun_; + Eigen::MatrixXd matrix_; +}; + + +/** + * \brief Static constructor of a linearly transformed function. + * + * @param[in] function The function to be linearly transformed. + * @param[in] matrix The transformation matrix. Its dimension should be d*d, + * where d is the domain (ambient) dimension of 'function'. + * + * \tparam Function_ The function template parameter. Should be a model of + * the concept FunctionForImplicitManifold. + */ +template <class Function_> +Linear_transformation<Function_> make_linear_transformation(const Function_& function, + const Eigen::MatrixXd& matrix) { + return Linear_transformation<Function_>(function, matrix); +} + +} // namespace coxeter_triangulation + +} // namespace Gudhi + +#endif |