How do I create a matrix C that is comprised of values from matrices A and B, using a nested for loop?

Hello, I have a question that says:

Where Cij is a 4x4 matrix and Cij= aij + bij for 1 =< i,j =< 2

aij - bij for 3 =< i,j =< 4

for all other values = 0

aij and bij are elements of the matrices A and B, use for loops.

Below i have given the matrices of A and B, I have also attempted this two ways, one includes a for loop but doesnt work. The other doesn't include a for loop but does work. Is there a way I can have it include a for loop and work haha, thanks for any help!

This way works, but no for loop:

code{A = [2 2 3 4; 1 0 1 1; 5 2 1 2; -1 2 -1 2];

B = [2 3 4 5; -1 0 2 2; 7 2 1 4; 2 0 1 2];

C = zeros(4);

a1 = A(1:2,1:2);

b1 = B(1:2,1:2);

a3 = A(3:4,3:4);

b3 = B(3:4,3:4);

add = A(1:2,1:2)+B(1:2,1:2);

sub = A(3:4,3:4)-B(3:4,3:4);

Z = zeros(2);

C = [add Z; Z sub]

% This way the code works but doesn't give the correct matrix for C, but i think something similar to this method is what the % quesiton is asking, includes for loop:

for A=1:2

for B=1:2

C(A,B)=A+B;

end

end

for A=3:4

for B=3:4

C(A,B)=A-B

end

end

% I'm sorry if it's an easy fix, any help is greatlu appreciated!

Answer 1

[Girijashankar Sahoo]

C=zeros(4)

A = [2 2 3 4; 1 0 1 1; 5 2 1 2; -1 2 -1 2];

B = [2 3 4 5; -1 0 2 2; 7 2 1 4; 2 0 1 2];

for i=1:4

j=1:2

C(i,j)=A(i,j)+B(i,j)

end

for i=1:4

j=3:4

C(i,j)=A(i,j)-B(i,j)

end

Answer 2

[Kartikay Sapra]

C = zeros(4)
A = reshape(1:16, 4, 4)
B = reshape(17:32, 4, 4)

C(1:2, 1:2) = A(1:2,1:2) + B(1:2,1:2);
C(3:4, 3:4) = A(3:4,3:4) - B(3:4,3:4);

C

You were on the right path!

Remember that indices while iterating i and j would be same for all A, B and C. So we can use the MATLAB matrix slicing properties.