How to identify array elements that occur more than once ?

For example D=[1 2 3 3 3 4 5 6 7 7 8]

I want to identify the elements that occur more than once.

The expected answer with respect to the above example Would be [ 3 7].

How do i do it in matlab. I can use for loop but i want to find out is there a better approach..

Answer 1

[KSSV]

Read about unique

find(hist(D,unique(D))>1)

[Stephen23]

This answer does not return the values as requested, e.g.:

>> D = [2 3 3 3 4 5 6 7 7 8];
>> find(hist(D,unique(D))>1)
ans =
   2   6

See my answer for the correct code.

Answer 2

[Stephen23]

>> U = unique(D);
>> U(1<histc(D,unique(D)))
ans =
   3   7

[Juan Velasquez]

Do you mind to explain this answer??