Why is my algorithm (detect corners of checker board) fail?

I=checkerboard(80,5,5);
I=I>0.5;
[imagePoints,boardSize] = detectCheckerboardPoints(I);
figure;
subplot(1,2,1);
imshow(I);hold on;
plot(imagePoints,'r+');
title('detectCheckerboardPoints method');

subplot(1,2,2);
plot(imagePoints,'r+');

Answer 1

[Matt Gaidica]

Do:

plot(imagePoints(:,1),imagePoints(:,2),'r+');

[Mahdi Noroozi]

Thanks very much...