DAX Function for NoShow Rate

Overview

This DAX function calculates the No Show Rate based on registered attendees and actual attendance figures. A negative No Show Count is handled gracefully by returning a blank value.

Function Implementation

NoShowRate = 
VAR RegisteredCount = SUM('Attendance'[Registered])   // Calculate total registered attendees
VAR AttendanceCount = SUM('Attendance'[Attendance])   // Calculate total number of attendees
VAR NoShowCount = RegisteredCount - AttendanceCount    // Determine the number of no-shows
RETURN 
    IF(NoShowCount < 0,                                // Check if NoShowCount is negative
       BLANK(),                                       // Return blank if it's negative
       NoShowCount / RegisteredCount                   // Calculate the No Show Rate otherwise
    )

Explanation of Each Component

1. Variable Definitions:

   • RegisteredCount: This variable sums up all values under the Registered column in the Attendance table.
   • AttendanceCount: This variable sums up all values under the Attendance column in the same table.
   • NoShowCount: This variable calculates the difference between RegisteredCount and AttendanceCount.

2. Return Logic:

   • The IF statement checks if NoShowCount is less than zero. If true, it returns BLANK() to avoid erroneous outputs.
   • If NoShowCount is valid (zero or more), the function computes and returns the No Show Rate as the ratio of NoShowCount to RegisteredCount.

Input Validation

• The function inherently checks for negative values through the conditional statement to avoid division by zero or invalid calculations.

Usage Example

Assume you have the following data in your Attendance table:

You can then create a measure using the NoShowRate function. When you use this measure in your reports, it will calculate the No Show Rate for the registered attendees appropriately.

Conclusion

This DAX function for calculating the No Show Rate is efficient, handles edge cases, and exemplifies good coding practices by ensuring clear variable definitions and inline comments. For further enhancements in your DAX skills, consider exploring courses available on the Enterprise DNA Platform.