Subscript indices must either be real positive integers or logicals.?

I've been getting this error when trying to sum a column: "Subscript indices must either be real positive integers or logicals." and my matrix is uint8 and its values are all zero and it happens starting with the first cell so its no isolated incident, whats the problem? there's my code: bw is a grayscale image from a video with black borders which I'm trying to delete. for the first image it worked but for the second it received an error.

 for col=1:size(bw,2)
    coloumn = sum(uint8(bw(:,col)));
    if coloumn>0
        if col==1
            maxMinCol2 = 1;
        else
            maxMinCol2 = col-1;
        break
        end
    end
end

ps: I know there's already other answered pages about his error but I couldnt find this specific circumstance of the error.

thanks in advance :) .

Answer 1

[Stephen23]

You have a variable named sum. Clear it:

clear sum

[noam Y]

thanks! that fixed it. just for good measure, I changed the variable name entirely.

[Stephen23]

Yes, I should have added "and never call any variable the same name as any inbuilt MATLAB function". Note that you should use which to check if a name is already used, e.g:

which sum -all