Count duplicates

Hi

I have a requirement to be able to count the duplicates in a table.

Eg

PrimaryKeyField   

1

2

3

3

4

5

5

6

7

So in this example the duplicate value would be 2, as both values 3 and 5 have multiple entries. 

This only ever needs to be calculated over the whole table and will only ever be in a single card visual, so row context is not a concern.

Cheers