MATLAB: Import same variable without overwrite

data importfor loop

I try to import one single point from 20 different mat file and save those point into a mat file without overwrite it. However my code keep overwritting it and only display the last value. Here is my code
for k = 1:20
  myfilename = sprintf('Image%d.mat', k);
  a = load(myfilename);
  newimg = (a.img -273);
  % The point of plants
  i = 100;
  j = 84;
  % Take the average of itself and all four of its neighboring 
  % values average each point in array  
  newimg(i,j) = 0.2*(newimg(i+1,j) + newimg(i-1,j) + newimg(i,j+1) + newimg(i,j-1) + newimg(i,j))
  val = newimg(i,j)
  newa = length(k);
  save('newa.mat','-append','val');
end

Best Answer

You are using the same variable name. If you want to append your new data, you have to store them in a new variable name. But its better if you create a cell array then each update of your data, the size of your cell array will increase
For example
for k=1:3
  a{k}=randi(4,4);
  save('file','a','-append')
end
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