??? Index exceeds matrix dimensions error in ploting data from a vector

Greetings. I got this error "??? Index exceeds matrix dimensions." when I run the loop function below.

    a ='C:\Users\Ace\Desktop\splash\';
    A =dir( strcat (a, '*.bmp' ));

 for icount = 1 : length( A )
    %load the background
    %icount = 1;

    buf = strcat(a, A(icount).name);
    im1 = imread (buf);

    %imshow(im1)

    %cut the temperature indicator at the right side
    [y, x, z] = size(im1);
    cutImg = im1(1:y , 1:320, :);
    %figure, imshow(cutImg)

    %cut the outter environment from the pool for an easier splash
    %detection.
    [y, x, z] = size(cutImg);
    cutImg2 = cutImg( yBound:y , 1:x, : );
    %figure, imshow(cutImg2)

    [y, x, z] = size(cutImg2);

    blackCount = 0;

     %count number of black pixel 
        for i = 1:x
            for j = 1:y
                R = uint16( cutImg2(j, i, 1) );
                G = uint16( cutImg2(j, i, 2) );
                B = uint16( cutImg2(j, i, 3) );
                if R == 0 && G == 0 && B == 0
                    blackCount = blackCount + 1 ;
                end
             end
        end

     %blackPixel percentage in an image
     blackB4 = blackCount / ( y * x ) * 100;

     % next image 

     buf = strcat(a, A(icount+1).name);
     im1 = imread (buf);

    %cut the temperature indicator at the right side
    [y, x, z] = size(im1);
    cutImg = im1(1:y , 1:320, :);
    %figure, imshow(cutImg)

    %cut the outter environment from the pool for an easier splash
    %detection.
    [y, x, z] = size(cutImg);
    cutImg2 = cutImg( yBound:y , 1:x, : );
    %figure, imshow(cutImg2)

    [y, x, z] = size(cutImg2);

    blackCount = 0;

     %count number of black pixel 
        for i = 1:x
            for j = 1:y
                R = uint16( cutImg2(j, i, 1) );
                G = uint16( cutImg2(j, i, 2) );
                B = uint16( cutImg2(j, i, 3) );
                if R == 0 && G == 0 && B == 0
                    blackCount = blackCount + 1 ;
                end
             end
        end

     %blackPixel percentage in an image
     blackAf = blackCount / ( y * x ) * 100 ;

     diff = blackAf - blackB4;

     if icount == 1;
         diffMax = [ diff ];
     else
         diffMax = [ diffMax ; diff ];
     end

end

 figure; plot( diffMax );

I suspect the error message comes from diffMax = [ diffMax ; diff ];

Or anyone can advise me? Or the error message comes from other part of the code? And the graph does not come out. Hope you can help me. Thanks.

[Sean de Wolski]

Please post the error message in its entirety. If this saves as a function it'll even tell you what line the error is on.

Also, don't name a variable 'diff' as this is a very useful built-in MATLAB function.

Answer 1

[Sean de Wolski]

The problem is that you're swapping y,x in your for-loops for blackcount.

You could of course vectorize the whole thing with:

blackcounts = sum(sum(all(~uint16(cutImg2),3)))