Power BI counting double values - powerbi

Question

I'm trying to create a measure in Power BI that will count doubles as a single value and then later add them all up to see how many doubles we have. Here is an example:
Each customer whose name shows up more than once should be counted as 1
Bonus question, how can I make a measure which will count customers whose name only shows up once (example name - Sarah).
Thanks in advance!

Answer 1

If you want to count the customers distinct you can use:
CountCustomers = DISTINCTCOUNT([Customer])
if you want to count the doubles, you can use:
Doubles = COUNTROWS(FILTER(SUMMARIZE(CusTable, CusTable[Customer], "countC", COUNTROWS(CusTable)), [countCol] > 1))
First I summarize it to a table with the name of the customer and how often it is appearing in the table
Next I filter this table by all rows bigger than 1
Last I count the rows

Answer 2

You can create this below measure to check the customer is there for once or multiple time in the list. This measure will return 1 if the customer is there for once and 0 if the customer exists for multiple time.
is_unique =
VAR current_customer = MIN(your_table_name[customer])
VAR customer_count =
CALCULATE(
COUNT(your_table_name[customer]),
FILTER(
ALL(your_table_name),
your_table_name[customer] = current_customer
)
)
RETURN IF(customer_count = 1, 1, 0)
This will return 1 for customer- Sarah and David. For all other customer, it will return 0. Now, if you add the above measure to a Card and apply SUM on the measure, it will return value 2 which is basically your customer count with single existence.