project_points_to_target_polynomial.hpp

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#pragma once
 
#include <array>
#include <span>
#include <vector>
 
#include "interpolation.hpp"
#include "least_squares_fit.hpp"
 
namespace kynema::math {
 
inline std::vector<std::array<double, 3>> ProjectPointsToTargetPolynomial(
    size_t num_inputs, size_t num_outputs, std::span<const std::array<double, 3>> input_points
) {
    // Calculate matrix of num_inputs points-based LSFE shape function values at ouput
    // locations
    const auto shape_functions = ComputeShapeFunctionValues(
        GenerateGLLPoints(num_outputs - 1), GenerateGLLPoints(num_inputs - 1)
    );
 
    // Project input_points to output locations using LSFE shape functions
    auto output_points = std::vector<std::array<double, 3>>(num_outputs);
    for (auto output : std::views::iota(0U, num_outputs)) {
        for (auto input : std::views::iota(0U, num_inputs)) {
            for (auto dim : std::views::iota(0U, 3U)) {
                output_points[output][dim] +=
                    shape_functions[input][output] * input_points[input][dim];
            }
        }
    }
    return output_points;
}
 
}  // namespace kynema::math