In our My Average Debug measure, we simply substitute the COUNTROWS function for the AVERAGEX function present in the My Average measure. Hence, when debugging our measure, we can essentially get information about the table that AVERAGEX is iterating over in order to understand whether the expected number of rows is being processed or not.
This technique can be used with any of the iterator functions, such as SUMX, AVERAGEX, COUNTX, and MEDIANX. In addition, this technique can also be used with any table created within a DAX expression. Understanding the properties of otherwise hidden, internal DAX tables can greatly aid in the troubleshooting and debugging of measure and column calculations.