MATLAB: How to count the number of vector elements without repetition

countrepetition

Hi, I have a vector that contains repeated elements, How can I count the number of vector elements without repetition?

For example: a=[2 5 2 8 9 8 7 8 1]; I expect the result will be: count = 6

>> na=[2 5 2 8 9 8 7 8 1];
>> length(unique(na))
ans =
   6
>>

If you convert to categorical, you can sort the counts by descending order:

a = randi(10,10,10);
histogram(categorical(a), 'DisplayOrder', 'descend');

One easy solution based on accumarray:

S = size(A);
[~,Y,Z] = ndgrid(1:S(1),1:S(2),1:S(3));
Y(:) = 1;
X = [repmat(B(:),S(3),1),Y(:),Z(:)];
C2 = accumarray(X,A(:),[],@mean)

And tested:

>> isequal(C2,C)
ans = 1