append_cell

box = cell(10, 10, 10);

for i = 1:10000
   loc = randi([1 10], [3 1]);
   value = randn(1);
   box{loc(1), loc(2), loc(3)} = [box{loc(1), loc(2), loc(3)}, {value}];
end
disp(box{1, 1, 1})
% [1.2534]    [1.5920]    [0.4901]    [-0.4669]    [-0.5213]    [-0.1594]
disp(sum(cell2mat(box{1, 1, 1})))
% 2.1879
box_sum = cellfun(@(x) sum(cell2mat(x)), box, 'UniformOutput', false);
disp(box_sum{1, 1, 1})
% 2.1879

box2 = cell(10, 10, 10);
for i = 1:10000
   loc = randi([1 10], [3 1]);
   value = randn(5);
   box2{loc(1), loc(2), loc(3)} = [box2{loc(1), loc(2), loc(3)}, {value}];
end
disp(box2{1, 1, 1})
% [5x5 double]    [5x5 double]    [5x5 double]    [5x5 double]    [5x5 double]    [5x5 double]    [5x5 double]    [5x5 double]
disp(sum(reshape(cell2mat(box2{1, 1, 1}), 5, 5, []), 3))
%    -0.2675   -3.1187    2.2361    1.7025    0.8923
%     1.9458   -3.8915    2.5633    1.9151    6.2906
%    -0.7282    2.9414   -4.2599    6.6166    1.5368
%    -6.4995    0.6097    0.4701    0.1814    1.4697
%     1.7196   -1.9204   -6.1786    2.0501    0.8797
box2_sum = cellfun(@(x) sum(reshape(cell2mat(x), 5, 5, []), 3), box2, 'UniformOutput', false);
disp(box2_sum{1, 1, 1})
%    -0.2675   -3.1187    2.2361    1.7025    0.8923
%     1.9458   -3.8915    2.5633    1.9151    6.2906
%    -0.7282    2.9414   -4.2599    6.6166    1.5368
%    -6.4995    0.6097    0.4701    0.1814    1.4697
%     1.7196   -1.9204   -6.1786    2.0501    0.8797