/// <summary>
/// A^TAx = A^b
/// </summary>
/// <param name="rhs"></param>
/// <returns></returns>
public VectorXD LeastSquaresNE(VectorXD rhs)
{
double[] vout = new double[Cols];
EigenDenseUtilities.NormalEquationsLeastSquares(GetValues(), Rows, Cols, rhs.GetValues(), vout);
return(new VectorXD(vout));
}