1 #include <Eigen/Dense>
2 #include <iostream>
3 
4 using namespace std;
5 
main()6 int main()
7 {
8   Eigen::MatrixXf m(4,4);
9   m <<  1, 2, 3, 4,
10         5, 6, 7, 8,
11         9,10,11,12,
12        13,14,15,16;
13   cout << "Block in the middle" << endl;
14   cout << m.block<2,2>(1,1) << endl << endl;
15   for (int i = 1; i <= 3; ++i)
16   {
17     cout << "Block of size " << i << "x" << i << endl;
18     cout << m.block(0,0,i,i) << endl << endl;
19   }
20 }
21