Storing information of last frames in real time video acquisition MATLAB

Question

This code processes a video in real time through a webcam in Matlab. For each frame, I perform some operations and the final result is 'degrees'.

I need to store the result of degrees for, let's say, the last 15 frames, and check that they are all in the same range (for example between 50 and 80 degrees), all this while the video is still running. But I would like to be deleting the previous ones in order to save memory (since it is video acquisition it can run forever), or if not possible how can I always compare with the last 15 frames?

    function DetectTarget2()
    clc;imaqreset;close all;

    try
        % For linux
        Vid = videoinput('linuxvideo', 1);
    catch
        try
            % For mac
            Vid = videoinput('macvideo', 1);
        catch
            errordlg('No webcam available');
        end
    end

    set(Vid,'FramesPerTrigger',1);  %capture 1 frame every time Vid is triggered
    set(Vid,'TriggerRepeat',Inf);   %infinite amount of triggers
    set(Vid,'ReturnedColorSpace','RGB');
    triggerconfig(Vid, 'Manual');   %trigger Vid manually within program

    t = timer('TimerFcn',@dispim, 'Period', 0.04,...
        'executionMode','fixedRate');

    function dispim(~,~)
            trigger(Vid)%trigger Vid to capture image
            im=getdata(Vid,1);
            detector = vision.CascadeObjectDetector('Cascade1Matlab.xml');
            bbox = step(detector, im); 

    % CALCULATIONS

    degrees=result;
    end
    end

Answer 1

No problem at all, use the modulo function to access cells in a cell array.

In somewhat pseudocode:

result_buffer = cell(1, 15);
index = 1;
while ~finished
  ... % some calculation
  result_buffer{mod(index, 15) + 1} = result;
  % access some previous result
  result_buffer{mod(index - 5, 15) + 1}; % the image of 5 iterations before
  index = index + 1;
end

This is a simple circular buffer.