#includeusing namespace Eigen; int main() { VectorXd x(3); x << 1, 2, 3; int size = x.size(); // size is 3 return 0; }
#includeThis example creates a zero-initialized VectorXd object with five elements. The size() function is used to obtain the number of elements, which is 5. In conclusion, VectorXd is a data type used in the Eigen library for representing mathematical vectors. The size() function in VectorXd is used to obtain the number of elements in the vector.using namespace Eigen; int main() { VectorXd x(5); x.setZero(); int size = x.size(); // size is 5 return 0; }