How to scan a matrix row by row and execute certain commands if conditions are met.

I have a Matrix ....

A =

12 0 0

0 0 0

0 13 0

0 0 0

0 0 0

0 0 11

I want to ...

Scan the first row of the matrix.

--> If any of the values in the row are > 0, then assign that value to 1, but keep the others as 0, and move to the next row.

--> However, if all of the values in the row equal 0, then look to see which of them immediately follow a value that is > 0. Replace that 0 with a 1. Keep the others as 0. Move to next row of the matrix.

Carry on with the steps above , until you reach last row of the matrix.

Therefore, Matrix A should look like this at the end:

A =

1 0 0

1 0 0

0 1 0

0 1 0

0 1 0

0 0 1

Thank you!

Answer 1

[Voss]

A =  [12    0     0
     0     0     0
     0    13     0
     0     0     0
     0     0     0
     0     0    11];
% scan each row of A
for ii = 1:size(A,1)
    % find the index of non-zero elements in the row
    idx = find(A(ii,:));
    % if there are none (the row is all zeros)
    if isempty(idx)
        % if it's not the first row
        if ii > 1
            % find the index of non-zero elements in the previous row
            idx = find(A(ii-1,:));
            % set the elements at those indices in this row to 1
            A(ii,idx) = 1;
        end
    else % if there are some non-zero elements in the row, set them to 1 
        A(ii,idx) = 1;
    end
end
A

A = 6×3

1 0 0 1 0 0 0 1 0 0 1 0 0 1 0 0 0 1

[Laura Steel]

Thank you very much! This works perfectly :)

[Voss]

You're welcome!