Count number of cases that happens once in a period
I'm facing an issue to find a expression that counts the number of ID's that happens only once in a period of days.
Example: in the last 15 days I have the following ID's appearing in a log file:
I can see that Y and Z appeared more than once in this period, so I need an expression that will give me the result equal to 3 (that is the number of IDs that only appeared once in this interval = X, W and K). Any ideas?