Hello, I have two matrices of different sizes and I want to find the indices for the elements in the bigger matrix that match with those in the smaller one, allowing for repetition?

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Alaa Hameed 2017-1-20

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评论： Alaa Hameed 2017-1-20

Hello, I have two matrices of different sizes and I want to find the indices for the elements in the bigger matrix that match with those in the smaller one, allowing for repetition? A=[1 1 1 2 3 5 5 1 ] B=[1 2 5] I want to get C=[1 2 3 4 6 7 8]

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Jorge Mario Guerra González 2017-1-20

For the forum order, try to summarize the title of the post into a shorter sentence. Check the answer I give you below.

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Answer 1

Image Analyst 2017-1-20

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Use ismember():

A=[1 1 1 2 3 5 5 1 ] 
B=[1 2 5] 
% Want C=[1 2 3 4 6 7 8]
[inA, inB] = ismember(A, B)
C = find(inA)

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Jorge Mario Guerra González 2017-1-20

yes, this is what I meant with a smarter way of doing it.

Alaa Hameed 2017-1-20

Thanks that was helpful

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Answer 2

Jorge Mario Guerra González 2017-1-20

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Hello Alaa, I believe the way to do it is just comparing array A with each element of B using find function. There must be a smarter way to it, but this example gives the output you want.

A=[1 1 1 2 3 5 5 1];
B=[1 2 5];
result=[];
for i=1:length(B)
  C=find(A==B(i));
  result=[result C]; %#ok<AGROW>
end
result=sort(result);
disp(result);