I am getting a block of a matrix like so:

Code: Select all

H.block(ii(0), ii(0), 2, lenx);

How do I go about assigning it to a local variable (which must be...? Eigen::Block?) so that I can work with that block now instead of typing out all that code every time. I have looked through the documentation and know how to pass it as a function argument, but how do I create a local variable of the block to store it temporarily and at the same time affect the original matrix when the block elements change?

As you can tell, I am also new to template programming, so this is confusing me a little bit

here you go:

Block<typeof_H> block_of_H = H.block(ii(0), ii(0), 2, lenx);

Excellent, thanks! Follow up question, what should I do in the following two cases:

1) I want the block to change the original matrix. So when I change the elements in the block, the original matrix reflects the change
2) I want the block to NOT change the original matrix

for case 1: see my previous reply

for case 2: copy the block to a temporary:

MatrixXd H;
// ...
MatrixXd block_of_H = H.block(ii(0), ii(0), 2, lenx);