MATLAB: How to remove unique values.

Question

Hi,

I have a vector with some repeating values, and some unique.

e.g. A = [ 1 1 2 4 4 3 4 1 5 3]

How do i remove the unique values and get this:

ans = [1 3 4]

i.e. if there are duplicates of a value, keep one copy of that value. uniques are not wanted.

i can easily use unique to remove the duplicates but i also want to remove the values that appeared once.

Thanks,

Danny

Answer 1

Assuming that elements of A are integers greater or equal to 1, you could do something like:

 >> nonUniqueValues = find( accumarray(A.', ones(size(A))) > 1 )
 nonUniqueValues =
     1
     3
     4

EDIT: we could also imagine an approach based on diff(sort(A))==0, but I prefer the approach above.