Hi all,

I would like to ask that how can I copy different colounms of a matrix pointing by another matrix ?

In Matlab, I do like this,

A = [1 2 3 4; 5 2 1 3; 2 3 4 1]; % 3X4 matrix
ind = [1 3 4]; % 1X3 matrix
B = A(:,ind)
% result of B
B = [1 3 4;5 1 3;2 4 1]

You can obtain similar results using this code :

Code: Select all

   MatrixXd A (3,4);

   A << 1, 2, 3, 4,
       5, 2, 1, 3,
       2, 3, 4, 1;

   VectorXi ind(3);

   ind << 0, 2, 3;

   MatrixXd B(A.rows(),ind.size());

   for(int i = 0 ; i < ind.size(); i++)
      B.col(i) = A.col(ind(i));


   cout << B;


I don't know if there is an easiest way to do that.

Thanks a lot