如何在Armadillo中根据行总数的条件删除SpMat<unsigned int>的行？

void shed_rows(arma::SpMat<eT>& X, const arma::uvec& rows_to_shed, const bool sort_indices = true);

#include <iostream>
#include <armadillo>

int main()
{
    // 创建一个稀疏矩阵
    arma::SpMat<unsigned int> mat(5, 3);
    mat(0, 0) = 1;
    mat(0, 1) = 2;
    mat(0, 2) = 3;
    mat(1, 0) = 4;
    mat(1, 1) = 5;
    mat(1, 2) = 6;
    mat(2, 0) = 7;
    mat(2, 1) = 8;
    mat(2, 2) = 9;
    mat(3, 0) = 10;
    mat(3, 1) = 11;
    mat(3, 2) = 12;
    mat(4, 0) = 13;
    mat(4, 1) = 14;
    mat(4, 2) = 15;

    // 打印原始矩阵
    std::cout << "原始矩阵：" << std::endl;
    std::cout << mat << std::endl;

    // 根据行总数的条件删除行
    arma::uvec rows_to_shed;
    for (arma::uword i = 0; i < mat.n_rows; ++i)
    {
        if (mat.row(i).n_nonzero > 2)  // 行总数大于2的条件
        {
            rows_to_shed.insert_rows(rows_to_shed.n_elem, i);
        }
    }
    mat.shed_rows(rows_to_shed);

    // 打印删除行后的矩阵
    std::cout << "删除行后的矩阵：" << std::endl;
    std::cout << mat << std::endl;

    return 0;
}