本文转载自Eigen中norm、normalize、normalized的区别
norm、normalize、normalized的区别
# include <eigen3/Eigen/Dense>
# include <iostream>
using namespace std;
using namespace Eigen;
int main(int argc, char *argv[])
{
Eigen::Vector3d vec(3,4,5);
cout << "data.norm() = " << vec.norm() << endl;
vec.normalize();
cout << "vec.normalize() = " << vec << endl;
cout << "vec.normalized() = " << vec.normalized() << endl;
Eigen::Matrix3d mat;
mat << 1,2,3,
4,5,6,
7,8,9;
cout << "mat.norm() = " << mat.norm() << endl;
mat.normalize();
cout << "mat.normalize() = " << mat << endl;
cout << "mat.normalized()" << mat.normalized() << endl;
return 0;
}
![在这里插入图片描述](https://img-blog.csdnimg.cn/474e65cef8454bfa8010fdf3e4b094dd.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2h1YW5nanVuc2hlbmcxMjM=,size_1,color_FFFFFF,t_70)
由以上示例可以发现
对于Vector,norm() 返回的是向量的二范数,即
![在这里插入图片描述](https://img-blog.csdnimg.cn/c28d1d85df0543c5a3699e1d7f74f27c.png)
对于Matrix,norm() 返回的是矩阵的弗罗贝尼乌斯范数(Frobenius Norm),即
![在这里插入图片描述](https://img-blog.csdnimg.cn/e829d09f8f7b40a498c503a4e2691651.png)
清楚了norm()的定义后,normalize() 其实就是把自身的各元素除以它的范数。返回值为void。
而 normalized() 与normalize()类似,只不过normalize()是对自身上做修改,而normalized()返回的是一个新的Vector/Matrix,并不改变原有的矩阵。