How to reset the size variable inside looping?

I have a loop, but the variable keep continuing. How could I set null variable without use clear or clear all

Example :

file_pattern = fullfile(folder,'truntum*.*');
thefile = dir(file_pattern);
% Access each image file
for k = 1 : length(thefile)
    baseFilename = thefile(k).name;
    fullFilename = fullfile(folder, baseFilename);
    picture = imread(fullFilename);
    BW = im2bw(picture);
    % Process the picture
    % Result : some detected object
    % For example, 14 object detected
    area(totalObject,1) = 0;
    % Save the area of each object
    % Then access some index, example area(2,1) area(3,1) area(7,1)
end

Variable area size is array 14 x 1. For the second looping (k=2), with different image, the total object detected is different. So, the size of variable area is different too. For the example, k=2 with totalObject = 7. It's less than the lastest total object. But, the size of area is still 14x1 and the value in index 8-14 still inside the variable. So, in k=2 index over the total object still working to access when it should be we could not access the index because the area size is 7x1.

Any idea what should I do to solve this problem? I tried to use clear all to reset all variables in workspace. But it make the k variable reseted and disturb the looping. Do you know to reset size of variable? Thank you

Answer 1

[Stephen23]

Best, most robust and clearest solution: define area explicitly not implicitly:

area = zeros(totalObject,1);

Slowest and untidiest solution: clear just that variable at the the of the loop:

clear area