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find a set of data in an array

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mahsa momtahan
mahsa momtahan on 31 Jan 2020
Commented: Ridwan Alam on 31 Jan 2020
Hi everyone,
I have an array of repetitive values something like A=[0;0;396; ...;140;... ;403; 0 ;0 ;0 ;200; 140; ...;403; 0; 0 ] . I extracted non-zero set of data to another array, called B=[396; ...;140;... ;403 , 200; 140; ...;403]. Now, I want to find the index of each set of elements of array B from array A, but when I use '[tf,idx] = ismember (B,A)' , what is happening is that for those repeated elements the index is always the same as the index of first appeared one (idx for second 140 or 403 is the same of the idx of the first ones!). So, my question is that how can I find the indexes based on order ? or how can I find indexes when all the elements of array B's columns exactly repeated in array A?
Thanks,
Mahsa

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Ridwan Alam
Ridwan Alam on 31 Jan 2020
maybe if you share your A and B and some sample code, it would be easier to help.

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Answers (2)

Ridwan Alam
Ridwan Alam on 31 Jan 2020
Edited: Ridwan Alam on 31 Jan 2020
idx = find(A~=0);
B = A(idx);
idx and B have the same size and order. I believe this is what you are looking for?

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mahsa momtahan
mahsa momtahan on 31 Jan 2020
No this won't work. I have a big data and as the exact time of appearing each element mattters, I cannot find out that the idx returned by 'idx = find(A~=0)' belongs to which elements (one data can be repeated so many times). I used regionprops(Data>Threshold, Data, 'PixelValues') to extract my data and need to find whole set of founded Pixelvalues in Data (for each i=1:xx, B(:,i) should be found in A).

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