Is there a way to check each index of a matrix against each index of another smaller matrix?

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Caroline F 2022-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/1701100-is-there-a-way-to-check-each-index-of-a-matrix-against-each-index-of-another-smaller-matrix

回答： Voss 2022-4-20

Is there a way to check each index of a matrix against each index of another smaller matrix? I am trying to create a code that will check the index of one matrix, A, and compare it to another matrix, B. I want to find a row vector in A where none of the index in that row are equal to any of the index in B. I was thinking of using a for loop and somehow incorporating the find() function, but I am not sure where to start. Any tips would be appreciated.

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Answer 1

Voss 2022-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/1701100-is-there-a-way-to-check-each-index-of-a-matrix-against-each-index-of-another-smaller-matrix#answer_947010

在 MATLAB Online 中打开

% a matrix:
A = magic(5)
A = 5×5
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
% a smaller matrix:
B = [1 15 6; 20 12 21; 25 2 9]
B = 3×3
     1    15     6
    20    12    21
    25     2     9
% index(es) of row(s) of A that have no elements in B:
find(~any(ismember(A,B),2))
ans = 2
% breaking that expression down a little bit:
ismember(A,B)
ans = 5×5 logical array
   0   0   1   0   1
   0   0   0   0   0
   0   1   0   1   0
   0   1   0   1   0
   0   0   1   1   1
any(ismember(A,B),2)
ans = 5×1 logical array
   1
   0
   1
   1
   1
~any(ismember(A,B),2)
ans = 5×1 logical array
   0
   1
   0
   0
   0