How can I count the number of vector elements without repetition?

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

Answer 1

[dpb]

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