1 #include <iostream>
2 #include <Eigen/Dense>
3 
4 using namespace std;
5 using namespace Eigen;
6 
main()7 int main()
8 {
9   Eigen::MatrixXf m(2,4);
10   Eigen::VectorXf v(2);
11 
12   m << 1, 23, 6, 9,
13        3, 11, 7, 2;
14 
15   v << 2,
16        3;
17 
18   MatrixXf::Index index;
19   // find nearest neighbour
20   (m.colwise() - v).colwise().squaredNorm().minCoeff(&index);
21 
22   cout << "Nearest neighbour is column " << index << ":" << endl;
23   cout << m.col(index) << endl;
24 }
25