// 矩阵操作
double          uM[9] = {0, 1,  2,
                           1, 1,  4,
                           2, -1,  0};
  double          uB[3][3] = {0, 1,  2,
                              1, 1,  4,
                              2, -1,  0};
  Eigen::Matrix3d Mat1;
  Mat1<<uB[0][0], uB[0][1], uB[0][2], uB[1][0], uB[1][1], uB[1][2], uB[2][0], uB[2][1], uB[2][2];
// Mat1<<uM[0],uM[1],uM[2],uM[3],uM[4],uM[5],uM[6],uM[7],uM[8];
// Mat1 <<0, 1,  2, 1, 1,  4, 2, -1,  0;
  cout << "Mat1逆矩阵：\n" << Mat1.inverse() << endl;
  cout << "Mat1逆矩阵第一个元素：\n" << Mat1.inverse()(0, 1) << endl;
  cout << "Mat1转置矩阵：\n" << Mat1.transpose() << endl;

// 向量操作

  Eigen::Vector3d a(1.0, 2.0, 3.0);// 默认为列向量  或者a(0) = 1; a(1) = 2; a(2)= 3;
  std::cout << "a = \n" << a << std::endl;

// 矩阵变化操作
 std::cout << "zx = \n" << Mat1*a << std::endl;