Counting blank results from a measure

[aflintdepm]

I have a set of data for customer appointments

Table 1 is the customer fact table (name, id, etc.)

Table 2 is the appointment data (id, appointment date, appointment status)

I have a measure that calculates the next future appointment

Measure =

CALCULATE(

    MIN('Appointments'[Appointment Date]),

    'Appointments'[Appointment Date]>=TODAY())

What I need is a way to count how many of the customers have no next appointment.  I can see who doesn't by using a table and making my measure one of the columns, but I need to count how many rows are blank for this value.

Thanks for any help.

[vicky_ · Accepted solution]

I'm going to assume that the id column links the two tables, but go ahead and substitute whatever you need.

Customers with no Next Appointment = 
var AllCustomers = VALUES(Table1[CustomerID])
var customersWithAppointment = SELECTCOLUMNS(FILTER(Table2, Table2[Appointment Date] >= TODAY()), 
    "customers", Table2[id])

RETURN COUNTROWS(EXCEPT(AllCustomers, customersWithAppointment))