exercise_2/colmap-build/eigen-eigen-323c052e1731/doc/snippets/EigenSolver_eigenvectors.cpp

MatrixXd ones = MatrixXd::Ones(3,3);
EigenSolver<MatrixXd> es(ones);
cout << "The first eigenvector of the 3x3 matrix of ones is:"
     << endl << es.eigenvectors().col(0) << endl;