#include#include using namespace Eigen; int main() { MatrixXd mat(3,3); // Create a 3x3 matrix mat << 1, 2, 3, 4, 5, 6, 7, 8, 9; VectorXd row = mat.row(1); std::cout << "Second row of matrix:\n" << row << std::endl; return 0; }
#includeThis code starts by creating a 9-dimensional vector and initializing it with values 1 to 9. Then it creates a 3x9 matrix by repeating the vector horizontally 3 times. Next, it creates a new 3-dimensional row vector and assigns it new values. Finally, it replaces the second row of the original matrix with the new vector, by using the row() method and assignment operator. The result is printed to the console. Package library: Eigen#include using namespace Eigen; int main() { VectorXd vec(9); // Create a 9-dimensional vector vec << 1, 2, 3, 4, 5, 6, 7, 8, 9; MatrixXd mat = vec.transpose().eval().replicate(3,1); // Create a 3x9 matrix of repeated rows std::cout << "Original matrix:\n" << mat << std::endl; VectorXd row(3); row << 10, 11, 12; mat.row(1) = row.transpose(); std::cout << "Modified matrix:\n" << mat << std::endl; return 0; }