——參考書《A Systematic Approach to Learning Robot Programming with ROS》

ROS中的資料操作需要線性代數，Eigen庫是C++中的線性代數計算庫。它獨立於ROS，但是在ROS中可以使用。在CMakeLists.txt檔案中要做以下配置

#uncomment the following 4 lines to use the Eigen library
find_package(cmake_modules REQUIRED)
find_package(Eigen3 REQUIRED)
include_directories(${EIGEN3_INCLUDE_DIR}
 
)
add_definitions(${EIGEN_DEFINITIONS})

在原始碼中要包含以下標頭檔案

#include <Eigen/Eigen>
#include <Eigen/Dense>
#include <Eigen/Geometry>
#include <Eigen/Eigenvalues>

定義一個向量：

Eigen::Vector3d normal_vec(1,2,3); // here is an arbitrary normal vector, initialized to (1,2,3) upon instantiation
 

將向量變成單位向量

normal_vec/=normal_vec.norm(); // make this vector unit length

定義一個矩陣的形式是：

Eigen::Matrix3d Rot_z;
Rot_z.row(0)<<0,-1,0;  // populate the first row--shorthand method
Rot_z.row(1)<<1, 0,0;  //second row
Rot_z.row(2)<<0, 0,1;  // yada, yada
cout<<"Rot_z: "<<endl;  

可以按行賦值。

矩陣與向量的乘法

v1 = Rot_z*normal_vec; 
//here is how to multiply a matrix times a vector
//although Rot_z and normal_vec are both objects (with associated data and member methods), multiplication is defined,
//resulting in the data members being altered or generated as expected for matrix-vector multiplies

行了，用到了再說吧，頭疼