On Mon, 9 Apr 2012 14:27:36 -0700 (PDT), jt wrote:

Hi there,
I have a column on numbers and I was wondering if I can add a formula
to the bottom of the column that would tell me how many dublicate
numbers there are.

thanks in advance for your time.

If you want a count of unique duplicates, in other words, if the sequence:

1
2
2
2
2
1
1

should return 2 (duplicate numbers = 1 and 2), then try:

=SUM(--(FREQUENCY(A:A,A:A)1))

If this sequence should return 5 (1 is duplicated twice; 2 is duplicated thrice), then use Isabelle's formula