modify parted matrix element

Hi i have part of specific matrix was made partition , then how we can modify all of element of this part by add or multiply or any mathematical operation??

[Andrew Newell]

Could you elaborate?

Answer 1

[bym]

x =magic(4)

x =

      16     2     3    13
       5    11    10     8
       9     7     6    12
       4    14    15     1

   x(1:2,1:2)=x(1:2,1:2)-x(1:2,1:2)

x =

       0     0     3    13
       0     0    10     8
       9     7     6    12
       4    14    15     1