Row and Column reduction of

I want to change matrix like below picture.

How can I do?

Thanks :)

Answer 1

[KSSV]

A = rand(4) 

A = 4×4

0.2474 0.1371 0.8875 0.6324 0.2656 0.0413 0.9122 0.4274 0.4822 0.9391 0.8935 0.8856 0.9399 0.0016 0.7617 0.4273

iwant = zeros(6) ; 
iwant(1:4,1:4) = A 

iwant = 6×6

0.2474 0.1371 0.8875 0.6324 0 0 0.2656 0.0413 0.9122 0.4274 0 0 0.4822 0.9391 0.8935 0.8856 0 0 0.9399 0.0016 0.7617 0.4273 0 0 0 0 0 0 0 0 0 0 0 0 0 0

B = iwant ;
iwant = B(1:4,1:4)

iwant = 4×4

0.2474 0.1371 0.8875 0.6324 0.2656 0.0413 0.9122 0.4274 0.4822 0.9391 0.8935 0.8856 0.9399 0.0016 0.7617 0.4273