Function eye

source/matplot/util/common.h:501–507

                                double min_radius = 1., double exponent = 0.5);

    template <class T = double> std::vector<std::vector<T>> eye(size_t n) {
        std::vector<std::vector<T>> r(n, std::vector<T>(n, static_cast<T>(0)));
        for (size_t i = 0; i < n; ++i) {
            r[i][i] = 1.;
        }
        return r;
    }

    MATPLOT_EXPORTS
    vector_2d transpose(const vector_2d &z);