how to split an 8x8 2D array

how would I split an 8x8 2D array into four 4x4 arrays so that I can take the mean of each 4x4 array using the mean function?

Answer 1

[Chetan Bhavsar]

Is this what you are looking for?

% Sample 8x8 array
A = reshape(1:64, [8,8])

A = 8×8

1 9 17 25 33 41 49 57 2 10 18 26 34 42 50 58 3 11 19 27 35 43 51 59 4 12 20 28 36 44 52 60 5 13 21 29 37 45 53 61 6 14 22 30 38 46 54 62 7 15 23 31 39 47 55 63 8 16 24 32 40 48 56 64

% Splitting into 4x4 arrays
A1 = A(1:4, 1:4)

A1 = 4×4

1 9 17 25 2 10 18 26 3 11 19 27 4 12 20 28

A2 = A(1:4, 5:8)

A2 = 4×4

33 41 49 57 34 42 50 58 35 43 51 59 36 44 52 60

A3 = A(5:8, 1:4)

A3 = 4×4

5 13 21 29 6 14 22 30 7 15 23 31 8 16 24 32

A4 = A(5:8, 5:8)

A4 = 4×4

37 45 53 61 38 46 54 62 39 47 55 63 40 48 56 64

% Computing the mean for each 4x4 array
mean_A1 = mean(A1(:));
mean_A2 = mean(A2(:));
mean_A3 = mean(A3(:));
mean_A4 = mean(A4(:));

% Displaying the results
fprintf('Mean of A1: %f\n', mean_A1);

Mean of A1: 14.500000

fprintf('Mean of A2: %f\n', mean_A2);

Mean of A2: 46.500000

fprintf('Mean of A3: %f\n', mean_A3);

Mean of A3: 18.500000

fprintf('Mean of A4: %f\n', mean_A4);

Mean of A4: 50.500000

[Freja]

yes thank you! also would there be a way to create a loop to index that and do each calculation for you?

[Chetan Bhavsar]

Yes we can use loop for splitting and Mean calculation

A = reshape(1:64, [8,8]);
mean_values = zeros(1, 4);

% Loop to extract 4x4 matrices and compute mean
for row = 1:2
    for col = 1:2
        r = (row-1)*4 + 1 : row*4;
        c = (col-1)*4 + 1 : col*4;
        
        submatrix = A(r, c);
        idx = (row-1)*2 + col;
        mean_values(idx) = mean(submatrix(:));
    end
end

for i = 1:4
    fprintf('Mean of A%d: %f\n', i, mean_values(i));
end

Mean of A1: 14.500000
Mean of A2: 46.500000
Mean of A3: 18.500000
Mean of A4: 50.500000