Like this:

Code: Select all

MatrixXd m(5,3);
VectorXd v(2);

//what I want to do is this, but this won't work
 m.leftCols(2).array()*v.array();
//or this won't work too
 ((m.leftCols(2)).matrix()).array()*v.array();

So I just do it this way:

Code: Select all

MatrixXd tmp = m.leftCols(2);
tmp.array()*v.array();


This one works but I think it's redundant, how to make the block a matirx on the fly?

hm, you're multiplying coefficient-wise a 5x2 sub-matrix with a 2x1 vector !!! that cannot work!

ggael wrote:hm, you're multiplying coefficient-wise a 5x2 sub-matrix with a 2x1 vector !!! that cannot work!

Ahh, yeah, I made a mistake.