MATLAB: Extract elements of a list using their indices

indiceslist

I have a list B which contains the indices of a classified elements and a bigger list A and I want to extract the elements of A using the indices in the list A.

Is there a simple way to do it ?

NB :

I used this line to get theses indices :

[sharedvals,idx] = intersect(A,B,'stable');

Thank you in advance for your answers.

Best Answer

The ‘sharedvals’ result should be what you want, however it returns the identified values without repitition. If you want all of them (asuming there are more than one of some of them), the ismember function might be more appropriate.

Note that more information would be helpful, including the reason you asked this, considering that intersect appears to do what you want.

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MATLAB: Find if a value in a column is greater than a number and exclude the entire row

If A is that matrix of data, first we can check the seventh column:

A = [...];
idx = A(:,7) > 1e-5;

and then remove those rows using logical indexing:

A(idx,: ) = [];

Or it is likely to be better to keep the original data matrix intact and simply use the index vector idx when you need to extract that particular subset of data. Note you can also invert the index to get the remaining rows:

A = [...];
B = A(~idx,:);

Creating and using indices to access subsets of data is often simpler and faster than actually altering the original data matrices, as it simplifies the memory management that MATLAB has to perform when you change the matrices.

MATLAB: How to reference index from list to contents of cell

Found the answer

>> [sharedvals,idx] = intersect(A,B,'sorted')

Best Answer

Related Solutions

MATLAB: Find if a value in a column is greater than a number and exclude the entire row

MATLAB: How to reference index from list to contents of cell

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