How to replace a subsection in a 5 x 5 matrix with a 4 x 2 matrix

I have a matrix: R55 = [2,4,6,9,11;7,8,9,10,6;1,2,6,4,5;,6,9,8,5,6;1,6,5,7,5];

I need to replace the subsection of elements starting from the element located on the 1st row and 3rd column, and ending at the element located on the 4th row and 4th column with all 1's and name it R55Mod.

I need to keep the original R55 matrix to perform further manipulations.

Thanks in advance!

Answer 1

[Voss]

 R55 = [2,4,6,9,11;7,8,9,10,6;1,2,6,4,5;,6,9,8,5,6;1,6,5,7,5];
 
 R55Mod = R55;
 R55Mod(1:4,3:4) = 1

R55Mod = 5×5

2 4 1 1 11 7 8 1 1 6 1 2 1 1 5 6 9 1 1 6 1 6 5 7 5