How does mat2cell work?

Hello,

I need your help understanding how cell2mat works. I have tried so hard, but I just don't get it.

I have:

• a Matrix called Matrix_A with a size of 18x46092.

I would like to:

• separate it so, that I get 15364 cells (this is the amount of points, 46092/3, for the x, y and z coordinates), each of these cells containing a 18x3 matrix (18 points each).

I have already done it with a line someone gave me. It is for the mean of Matrix_A. It works.

Matrix_A  = transpose(mat2cell(mean(cell2mat(Matrix_A)), 1, 3*ones(size(Matrix_A,2),1)));

Can someone please explain how cell2mat works, so that I can use it myself? A solution (a line of code) solves the problem right now, but this is the second or third time I want to do this and can't. That's why I would prefere an easy to understand explanaition.

Thank you!

Edit: I cannot post the Matrix_A data as it is too big.

Answer 1

[Steven Lord]

Let's try this with a slightly smaller matrix, so you can see what's going on.

A = reshape(1:24, [3 8])

A = 3×8

1 4 7 10 13 16 19 22 2 5 8 11 14 17 20 23 3 6 9 12 15 18 21 24

Let's slice this into 3-by-2 chunks. We don't actually need to slice it row-wise (since we want each chunk to have 3 rows just like A has three rows) but we do need to slice it column-wise.

rowSliceSizes = 3; % Each cell has three rows like A does
columnSliceSizes = [2 2 2 2]; % Each cell contains 2 columns of A

Now slice.

C = mat2cell(A, rowSliceSizes, columnSliceSizes)

C = 1x4 cell array
    {3×2 double}    {3×2 double}    {3×2 double}    {3×2 double}

celldisp(C)

 
C{1} =
 
     1     4
     2     5
     3     6

 
 
C{2} =
 
     7    10
     8    11
     9    12

 
 
C{3} =
 
    13    16
    14    17
    15    18

 
 
C{4} =
 
    19    22
    20    23
    21    24

 

Now let's slice A into a 2-by-3 cell array. Each cell in the first row of the result should contain 2 rows of A and each cell in the second row should contain the third row of A. Each cell in a column of the result contains 3, 2, and 3 columns of A respectively:

D = mat2cell(A, [2 1], [3 2 3])

D = 2x3 cell array
    {2×3 double}    {2×2 double}    {2×3 double}
    {1×3 double}    {1×2 double}    {1×3 double}

celldisp(D)

 
D{1,1} =
 
     1     4     7
     2     5     8

 
 
D{2,1} =
 
     3     6     9

 
 
D{1,2} =
 
    10    13
    11    14

 
 
D{2,2} =
 
    12    15

 
 
D{1,3} =
 
    16    19    22
    17    20    23

 
 
D{2,3} =
 
    18    21    24

 

[Diego Hens]

Thank you so much for your long and detailed answer. I have understood it and have applied it to my work.

Thank you for helping me to understand it and for not telling me the answer beforhand.

I am confident I will be able to correctly use this command next time.

Thanks!