Reference to a cleared variable

Hi friends,

After I runned the following program(part of all):

for l = 153:1:227
   figure;
   QQ = mouse(:,:,l);
   imshow(QQ,[]);
   hold on;
   seg_result(:, 3) = round(seg_result(:, 3));
   for i = 1:1:1519
     if seg_result(i, 3) == l
        plot(seg_result(i, 2),seg_result(i, 1),'.');
        hold on;
     end
   end
   for j = 1:1:1510
     if I(j, 3) == l
        plot(I(j, 2),I(j, 1),'.r');
     end
   end
 end

I saw an error:

Reference to a cleared variable seg_result.

Error in segment seg_result(:, 3) = round(seg_result(:, 3));

Please help me if you can deal with it,thank you!