How to adjust matrix

I have a 21x21 matrix. I want to remove the first two colums and rows, and the 11th and 12th columns and rows (resulting in a 17x17 matrix). How should I do this?

Answer 1

[Walter Roberson]

tokeep = [3:10, 13:21];
B = A(tokeep, tokeep);

or

B = A;
B(:,11:12) = []; B(11:12,[]) = [];
B(1:2,:) = []; B(:,1:2) = [];

Always delete the higher-index before the lower index.

[Voss]

Or delete all indices at once:

B = A;
B(:,[1 2 11 12]) = [];
B([1 2 11 12],:) = [];