How to compare 2 rows with specific row gap

I have a matrix called myMatrix. In the below code I generated a 256 bit response by comparing ROW1 with ROW2, ROW3 with ROW4 etc.

How can I modify the code to generate a 256 bit response by comparing ROW1 with ROW17, ROW2 with ROW18 etc.

output_bit=zeros(256,193);
for s=1:193;
    p=1;
for q=1:2:512; 
    
   if  myMatrix(q,s) > myMatrix(q+1,s);
        output_bit(p,s)=1;
   else 
       output_bit(p,s)=0;
       
   end
    p=p+1;
   
end 

end

Answer 1

[Guillaume]

In matlab loops are rarely needed and often make the code more complicated. Case in point, your original code comparing pairs of consecutive rows could be replaced by just:

output_bits = MyMatrix(1:2:end, :) > MyMatrix(2:2:end, :);

With your new question, what should happen after you've compared row 16 with row 32? Compare row 17 with row 33 or skip to comparing row 33 with row 49?

[Farhan K]

It should skip because the row compare should be in pairs.

[Farhan K]

I tried by replacing the new code. it works but it shows error in the later part of my full code. So I have to stick to the loop thing :(

[Guillaume]

My code above will work as long as MyMatrix has an even number of rows. If it's not the case, you need to explain what should happen with the extra pair-less row.

Which brings the next question for the skip-16. What should be done if the matrix height is not a multiple of 32?

[Farhan K]

It has even number of rows. Can you please help on how to compare ROW1 with ROW17, ROW2 with ROW18 etc as pairs using your code then?

[Image Analyst]

Did you try

output_bits = MyMatrix(1:2:end-17, :) > MyMatrix(17:2:end, :);

[Farhan K]

I tried this but the answer is not matching, something might be wrong

[Guillaume]

With no answer to my question "What should be done if the matrix height is not a multiple of 32", I'm assuming that the matrix height is a multiple of 32. In that case:

assert(mod(size(MyMatrix, 1), 32) == 0, 'Matrix height is not a multiple of 32');
temp_matrix = reshape(MyMatrix, 16, [], size(MyMatrix, 2));  %reshape into 16 rows, and move columns into the 3rd dimension
output_bits = reshape(temp_matrix(:, 1:2:end, :) > temp_matrix(:, 2:2:end, :), [], size(MyMatrix, 2)); %compare pair of columns along 3rd dimension (originally 2nd) and reshape back into matrix

[Farhan K]

It worked man!!! Wow thanks a lot bro :D