MATLAB: How to convert a 2D array 1632×11 to a 3D array 32x11x51

arraymatrix arraymultidimesional array

I have '1632×11' array and I would like to convert it to '32x11x51' array such that the values (32×11) after every 32 rows move to next page (thereby creating 51 pages) in an identical order as in 2D matrix i.e the values in row 33 of the 2D array become the values of row1 of page 2 in 3D array and so on.

I tried reshape, permute with reshape functions, these functions created the arrays but the results are not that I would like to have.

It would be really appreciated if someone can help me with this issue.

Best Answer

It will work with reshape and permute. I guess you want this:

X = rand(1632, 11);
Y = permute(reshape(X, 32, 51, 11), [1, 3, 2]);

If you want something else, simply play with the order. For some results an initial permutation (e.g. a transpose) is required.

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MATLAB: Converting 2d matrix to 3d

HI Joe,

if I'm not mistaken, it should be

permute(reshape(X, 512, 140, 8), [1 3 2]);

Titus

MATLAB: How to effectively get the mean for every three consecutive outputs

It would be useful if you used proper formatting in your question so we can see actual rows and columns.

Assuming the array

data = [1 10 19 28
        2 11 20 29
        3 12 21 30
        4 13 22 31
        5 14 23 32
        6 15 24 33
        7 16 25 34
        8 17 26 35
        9 18 27 36]

The mean of each block of 3 consecutive rows can be obtained by reshaping the matrix into a 3D arrays with 3 rows:

data3d = reshape(data, 3, [], size(data, 2))

Notice that the columns are now in the 3rd dimension. We can swap the dimensions to make taking the mean easier, by moving 1st dimension into 3rd, 3rd back to 2nd and 1st to second:

data3d = permute(data3d, [2 3 1])

Taking the mean across the pages, you get your result:

datamean3 = mean(data3d, 3)

Or as a one liner:

datamean3 = mean(permute(reshape(data, 3, [], size(data, 2)), [2 3 1]), 3)

Best Answer

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MATLAB: How to effectively get the mean for every three consecutive outputs

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