# Divide Matrix into smaller matrices

조회 수: 6 (최근 30일)
Max Reichert 2018년 2월 1일
답변: Walter Roberson 2024년 7월 30일
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.

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### 답변 (2개)

Sumukh 2024년 7월 30일
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 “dispfunction:
% disp(arr_20_2+"\n"); % Any post-processing……
More about the “reshape” function can be found here:
I hope this resolves your difficulty.
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Walter Roberson 2024년 7월 30일
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.

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