How to find numbers in one vector but not in the other vector?

For example, I have two vectors a=[2 3 4 6], and b=[3 4 5]. How do I find the index in a indicating the numbers that are not in b. In this example, a(1)=2 is not in b, a(3) = 6 is not in b either. So, the answer should be [2 4]. Is there a faster way doing this than using a full loop checking on each number?

[Azzi Abdelmalek]

The answer should be [2 6]

Answer 1

[Azzi Abdelmalek]

value=setdiff(a,b)

If you want values and index

[value,idx]=setdiff(a,b)