You should try to avoid dynamic variables names like a1, a2, ... and use arrays. Read here why: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
For example, here you can use cell arrays
imgset = imageSet('dataset');
imgs = cell(1, imgset.Count);
for i=1:numel(imgs)
imgs{i} = read(imgset, i);
end
and then you can access the image using brace indexing
imshow(imgs{1});
imshow(imgs{2});
