Modify the code from the previous example

clear, close all;
% Activity problem 6
 
% First example. With a loop, no ligical indexing.
 
N=6;
%NxN magic square
A=magic(N);
%Initialise B to be the same size as A with ones
B=ones(N);
 
%Set B to one where A is divisible by 3
%Loop over all elements
for row=1:N
    for col=1:N
        %Get current elemnet's value.
        value=A(row,col);
        %Is it a multiple of 3:
        if (mod(value,3)==0)
            B(row,col)=0;
        end
    end
end
 
disp(B)
 
% Second example, use logical indexing.
 
N=6;
A=magic(N)
 
B=ones(N);
indices=mod(A,3)==0;
B(indices)=0;
 
disp(B)
 
% part c
 
B(mod(A,3)==0)=0;

Now, based on the practice above, modify the code so that it starts with a magic square of size 5x5 and produces a second array that has a value of one where the magic square element is odd and a value of 2 where the corresponding magic square element is even.

[Walter Roberson]

What is your question?

Hint: if C is a value that is either 0 or 1, then A + (B-A)*C will give a value that is either A or B.

[Abigail McGahey]

i need to change to above code to follow the following criteria: it starts with a magic square of size 5x5 and produces a second array that has a value of one where the magic square element is odd and a value of 2 where the corresponding magic square element is even.

[Walter Roberson]

Your code builds an NxN magic square. If you want a 5 x 5 square specifically, then perhaps you should change N to be 5.

Note that restating a problem is not asking a question. A question might be something like,

"When I ran this code, on line 17, which is ...., it tells me that I have a subscript out of range. Could someone explain what that means?"

[Abigail McGahey]

okay, so to be more clear, I am struggling to figure out how to replace the odd elements with one and the even elements with the value of two.

[Walter Roberson]

"I am struggling" is not a question. A question might be something like how to write loops, or how to detect that a value is odd or even.

Answer 1

[Pranjal Priyadarshi]

The code below takes a magic square of size 6 and replaces the even elements with 2 and replaces the odd elements with 1.

N=6;
A=magic(N);
evenindex=(mod(A,2) == 0); %finds the index for even elements
finalans=A;
finalans(evenindex)=2; %replaces even elements with 2
finalans(~evenindex)=1; %replaces odd elements with value 1
disp(A);
disp(finalans);