How to find the indeces of same values within two vectors with repetitive values?

>> A = [1000,2000,2000,5000,20000,20000];
>> B = [1000,2000,2000,5000,10000,20000,20000,60000,60000,60000,60000,0,0,0,0,0,0,0,0,0,0,0,0,0];
>> X = A(:)==B; % requires MATLAB >=R2016b, for earlier versions replace == with BSXFUN.
>> [~,Y] = find(X & cumsum(X,2)==cumsum(X,1))
Y =
   1
   2
   3
   4
   6
   7

The example data from your comment:

>> A = [500,500,5000];
>> B = [250,500,500,1250,2500,5000,5000,15000,15000,15000,15000,8166,8926,9796,10800,11967,13333,14948,16875,16875,19200,22041,22041,25562];
>> X = A(:)==B; % requires MATLAB >=R2016b, for earlier versions replace == with BSXFUN.
>> [~,Y] = find(X & cumsum(X,2)==cumsum(X,1))
Y =
   2
   3
   6

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Valentina Mazzoni 2020-5-13

Thank you Stephen, it's the second time that you save me!! It works perfectly!!

Akihumi 2020-5-13

Wow that's a brilliant way to do it Stephen! Amazing!

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Answer 2

Mario Malic 2020-5-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/525117-how-to-find-the-indeces-of-same-values-within-two-vectors-with-repetitive-values#answer_432211

在 MATLAB Online 中打开

Values=ismember(B,A) % Will return true/false for each value of B found in A
Ind_Values = Values .* [1:1:length(B)] % Multiply it by a vector to get actual indices from B
Ind_Values = nonzeros(Ind_Values)' % Remove zeros 

Certainly, there is more elegant way to do this.

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Mario Malic 2020-5-13

编辑：Mario Malic 2020-5-13

在 MATLAB Online 中打开

Akihumi's answer is great. Maybe you can add if condition to his code to remove extra numbers?

Another suggestion is a function intersect, but it requires that matrix A does not have the same values, otherwise it will not work as you want.

[C,ia,ib] = intersect(A,B) %ib contains indices in B

Valentina Mazzoni 2020-5-13

Thank you very much Mario, I've already tried with intersect as you suggest but it didn't work as I wanted. Stephen Cobeldick's code is what I need. Thank you for your time!

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Answer 3

Akihumi 2020-5-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/525117-how-to-find-the-indeces-of-same-values-within-two-vectors-with-repetitive-values#answer_432218

编辑：Akihumi 2020-5-13

在 MATLAB Online 中打开

flip it to another way should work:

idx = find(ismember(B,A)==1);

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Valentina Mazzoni 2020-5-13

Thank you Akihumi, your code works perfectly too with the vectors in the question but if I change them, I obtain the same result that I have with Mario's code. Of course if you have any ideas, I'll be very happy to read them.

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