C++ Eigen Library - c++

Question

I'm having trouble compiling this program with #include. I see that if I comment out this line it compiles.
MatrixXd A = (1.0 / (double) d) * (p * U * p.transpose() - (p * u) * (p * u).transpose()).inverse();
I am unable to change the header since I need to run this code in ROS and I have to use the Eigen library built within. I am using the code as described in this link
How to fit a bounding ellipse around a set of 2D points.
Any help is greatly appricated.
pound include iostream
pound include Eigen/Dense
using namespace std;
using Eigen::MatrixXd;
int main ( )
{
//The tolerance for error in fitting the ellipse
double tolerance = 0.2;
int n = 12; // number of points
int d = 2; // dimension
MatrixXd p(d,n); //Fill matrix with random points
p(0,0) = -2.644722;
p(0,1) = -2.644961;
p(0,2) = -2.647504;
p(0,3) = -2.652942;
p(0,4) = -2.652745;
p(0,5) = -2.649508;
p(0,6) = -2.651345;
p(0,7) = -2.654530;
p(0,8) = -2.651370;
p(0,9) = -2.653966;
p(0,10) = -2.661322;
p(0,11) = -2.648208;
p(1,0) = 4.764553;
p(1,1) = 4.718605;
p(1,2) = 4.676985;
p(1,3) = 4.640509;
p(1,4) = 4.595640;
p(1,5) = 4.546657;
p(1,6) = 4.506177;
p(1,7) = 4.468277;
p(1,8) = 4.421263;
p(1,9) = 4.383508;
p(1,10) = 4.353276;
p(1,11) = 4.293307;
cout << p << endl;
MatrixXd q = p;
q.conservativeResize(p.rows() + 1, p.cols());
for(size_t i = 0; i < q.cols(); i++)
{
q(q.rows() - 1, i) = 1;
}
int count = 1;
double err = 1;
const double init_u = 1.0 / (double) n;
MatrixXd u = MatrixXd::Constant(n, 1, init_u);
while(err > tolerance)
{
MatrixXd Q_tr = q.transpose();
cout << "1 " << endl;
MatrixXd X = q * u.asDiagonal() * Q_tr;
cout << "1a " << endl;
MatrixXd M = (Q_tr * X.inverse() * q).diagonal();
cout << "1b " << endl;
int j_x, j_y;
double maximum = M.maxCoeff(&j_x, &j_y);
double step_size = (maximum - d - 1) / ((d + 1) * (maximum + 1));
MatrixXd new_u = (1 - step_size) * u;
new_u(j_x, 0) += step_size;
cout << "2 " << endl;
//Find err
MatrixXd u_diff = new_u - u;
for(size_t i = 0; i < u_diff.rows(); i++)
{
for(size_t j = 0; j < u_diff.cols(); j++)
u_diff(i, j) *= u_diff(i, j); // Square each element of the matrix
}
err = sqrt(u_diff.sum());
count++;
u = new_u;
}
cout << "3 " << endl;
MatrixXd U = u.asDiagonal();
MatrixXd A = (1.0 / (double) d) * (p * U * p.transpose() - (p * u) * (p * u).transpose()).inverse();
MatrixXd c = p * u;
cout << A << endl;
cout << c << endl;
return 0;
}

Answer 1

If I replace the obvious pound include bogus by
#include <iostream>
#include <Eigen/Dense>
it compiles just fine. It also runs, prints some numbers and returns 0.