Divide Matrix into smaller matrices

Hi, I have a problem regarding a matrice into smaller matrices. Basically I have a Matrix A (1000 x 2 double) which I want to subdivide into matrices with the dimension of 20 x 2. Thereby I want to maintain the value pairs in the matrices. Maybe this helps to understand what I Mean Original Matrix:

A = a1,1 a1,2
    a2,1 a2,2
    ... ...
    a1000,1 a1000,2

After the transformation the resulting matrices should look like this:

A_new1 = a1,1 a1,2
         a2,1 a2,2
         ... ...
         a20,1 a20,2

A_new2 = a21,1 a21,2
         a22,1 a22,2
         ... ...
         a40,1 a40,2
until

A_new50 = a981,1 a981,2
         a982,1 a982,2
         ... ...
         a1000,1 a1000,2

I tried to use to use reshape, but was not successful. Maybe somebody has an idea. Thanks in advance.

Answer 1

[Sumukh]

Hi Max.

To divide the matrix into multiple matrices, please check out the following code:

arr_temp=1:2000; % To store the 2000 numbers, taking 1:2000 numbers for easy understanding. 
arr_1000_2=reshape(arr_temp,[1000,2]); % Reshaping the date into array of size 1000x2. 
arr_20_2=zeros(20,2); % Declaring an array of size 20x2 to display the arrays

% For-loop to display the 20x2 arrays derived from 1000x2 array:
for i=1:20:1000 % 1000 rows, leaping 20 at a time
    arr_20_2=arr_1000_2(i:i+20-1,:); % Accessing every group of 20 rows from beginning and two column data.
    %     disp(arr_20_2+"\n"); % Any post-processing on the 20x2 array can be done here.
end
disp(arr_20_2); % Just displaying the last matrix, as output is too long.

         981        1981
         982        1982
         983        1983
         984        1984
         985        1985
         986        1986
         987        1987
         988        1988
         989        1989
         990        1990
         991        1991
         992        1992
         993        1993
         994        1994
         995        1995
         996        1996
         997        1997
         998        1998
         999        1999
        1000        2000

Array-indexing using the “:” operator allows us to access multiple rows and columns at a time. The above code uses a for-loop to iterate through the big matrix and divide it into smaller matrices. Any post-processing for the smaller matrices can be done within the loop itself, by replacing the commented out “disp” function:

    %     disp(arr_20_2+"\n"); % Any post-processing…… 

More about the “reshape” function can be found here:

https://www.mathworks.com/help/matlab/ref/reshape.html

I hope this resolves your difficulty.

Answer 2

[Walter Roberson]

A_cell = mat2cell(A1000_Matrix, 20*ones(1,size(A1000_Matrix,1)/20)), size(A1000_Matrix,2));

Now access A_cell{1}, A_cell{2} and so on.