I have 100 2D matrix .. After each matrix, I calculate the sum of elements inside it .. I want to see only the matrices with summation result under certain value (such as: 23). How can I do this?

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Mahmoud Ahmed
Mahmoud Ahmed 2017-5-10
编辑： Stephen23 2017-5-10
I have 100 2D matrix .. After each matrix, I calculate the sum of elements inside it .. I want to see only the matrices with summation result under certain value (such as: 23). How can I do this?
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Stephen23
Stephen23 2017-5-10
@Mahmoud Ahmed: storing them as separate variables is not a good way to write code. It will make your code slow, buggy, complicated, and hard to debug:
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
The best solution is to store your data in one 3D array. Then your task is trivially easy using indexing.

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回答（3 个）

Star Strider
Star Strider 2017-5-10
编辑：Star Strider 2017-5-10
I have no idea how your matrices are stored or organised.
One approach:
M3 = randi(3, 5, 5, 10); % Create Data
N = size(M3,3);
for k1 = 1:N
MN = M3(:,:,k1); % Define Matrix For This Loop Iteration
Msum = sum(MN(:)); % Matrix Sum
Mtx(k1) = k1 * (Msum < 23); % Save Index If ‘Msum < 23’, Else 0
end
James Tursa
James Tursa 2017-5-10
编辑：James Tursa 2017-5-10
E.g., if they were stored in a 3D array:
>> m = randi(10,3,3,5) % some random data
m(:,:,1) =
5 8 7
5 8 7
7 3 2
m(:,:,2) =
2 4 8
5 6 3
10 3 6
m(:,:,3) =
7 6 3
9 2 9
10 2 3
m(:,:,4) =
9 4 7
3 2 5
10 3 4
m(:,:,5) =
9 10 8
6 3 4
6 8 6
>> x = sum(reshape(m,[],size(m,3)))<50 % logical indexes where 2D sum is < 50
x =
0 1 0 1 0
>> s = m(:,:,x) % the 2D subsets that have the desired sum
s(:,:,1) =
2 4 8
5 6 3
10 3 6
s(:,:,2) =
9 4 7
3 2 5
10 3 4
Stephen23
Stephen23 2017-5-10
编辑：Stephen23 2017-5-10
Well, this is trivial if you store your data correctly in one array:
>> A = randi(8,2,2,100); % one hundred 2x2 matrices
>> idx = sum(sum(A,1),2)>23;
>> A(:,:,idx)
ans(:,:,1) =
7 2
8 8
ans(:,:,2) =
8 2
8 8
ans(:,:,3) =
4 7
8 8
ans(:,:,4) =
8 7
3 7
ans(:,:,5) =
8 4
8 4
ans(:,:,6) =
5 7
5 7
ans(:,:,7) =
3 8
8 5
ans(:,:,8) =
1 8
8 7
ans(:,:,9) =
4 6
7 8
ans(:,:,10) =
8 5
5 7
ans(:,:,11) =
8 7
6 4
ans(:,:,12) =
7 6
8 3

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