Find unique values in a sequence containing at least 3 elements

I want to find the unique values for each sequence containing minimum 3 repeating elements in a vector. For example, consider the vector:

x = [1 2 2 3 4 4 4 5 6 6 6 6 7 7 7 8];

The output (unique values) should be:

y = [4 6 7];

How can I achieve this?

Answer 1

[Niels]

u = unique(x);
a = histc(x,u);
y = u(a>=3);

This should do the trick. First determine the unique values in the vector, then count the number of times they occur. Then consider only the values that occur more than 2 times.

[Adrian]

Thank you very much. It works.