Code Explanation for ActualLast12Month

This code snippet is written in DAX (Data Analysis Expressions), a formula language used in various Microsoft products, such as Power BI, to define custom calculations in data models.

Breakdown of the Code

Variable Definitions

1. vYearMonthNumberLast12Mth:

   var vYearMonthNumberLast12Mth = CALCULATE(MAX('Calendar'[YearMonthNumber]),FILTER('Calendar','Calendar'[Date] = DATEVALUE(TODAY() - 360)))

   • Purpose: This variable calculates the maximum YearMonthNumber from the Calendar table for the date exactly 360 days before today.
   • Components:
     • CALCULATE(): This function modifies the filter context of data to execute a calculation.
     • MAX('Calendar'[YearMonthNumber]): It retrieves the highest YearMonthNumber value available in the filtered data.
     • FILTER('Calendar', 'Calendar'[Date] = DATEVALUE(TODAY() - 360)): This filter restricts the data to the row where 'Date' equals the date 360 days before the current date.

2. vYearMonthNumberActual:

   var vYearMonthNumberActual = CALCULATE(MAX('Calendar'[YearMonthNumber]),FILTER('Calendar','Calendar'[Date] = DATEVALUE(TODAY() - 30)))

   • Purpose: This variable finds the maximum YearMonthNumber from the Calendar table for the date exactly 30 days prior to today.
   • Components:
     • The structure is very similar to vYearMonthNumberLast12Mth, but it applies a different filter for a date that is 30 days before the current date.

Conditional Return Logic

3. Return Statement:

   RETURN
   IF('Calendar'[YearMonthNumber] >= vYearMonthNumberLast12Mth && 'Calendar'[YearMonthNumber] <= vYearMonthNumberActual, 1, 0)

   • Purpose: This statement evaluates whether each YearMonthNumber in the Calendar table falls within the last 12 months (from 360 days ago to 30 days ago).
   • Components:
     • IF(condition, true_value, false_value): This function checks a condition and returns true_value if the condition is met and false_value otherwise.
     • 'Calendar'[YearMonthNumber] >= vYearMonthNumberLast12Mth && 'Calendar'[YearMonthNumber] <= vYearMonthNumberActual: This condition checks if the YearMonthNumber is between the two variables defined above.
     • If the condition returns true, it outputs 1 (indicating the date is within the last 12 months); otherwise, it outputs 0.

Key Concepts Explained

• DAX Functions:

  • CALCULATE(): A highly versatile function that facilitates the evaluation of expressions in a modified filter context. This is essential for dynamic aggregations in data models.
  • MAX(): A simple aggregation function that returns the highest value of a column after applying any filters.
  • FILTER(): This function returns a table that represents a subset of another table, filtered by a specified condition.

• Date Manipulation:

  • The use of TODAY() generates the current date, and by subtracting days from it (360 and 30), the code dynamically calculates date ranges relative to the present day.

Additional Examples

Here are variations that illustrate similar concepts:

• Calculating Last 6 Months:

  var vYearMonthNumberLast6Mth = CALCULATE(MAX('Calendar'[YearMonthNumber]),FILTER('Calendar','Calendar'[Date] = DATEVALUE(TODAY() - 180)))
  var vYearMonthNumberActual = CALCULATE(MAX('Calendar'[YearMonthNumber]),FILTER('Calendar','Calendar'[Date] = DATEVALUE(TODAY() - 30)))

• Using Different Conditions:

  RETURN
  IF('Calendar'[YearMonthNumber] >= vYearMonthNumberLast6Mth && 'Calendar'[YearMonthNumber] <= vYearMonthNumberActual, "Active", "Inactive")

In these variations, the time frame or return values can be adjusted, demonstrating different analytical scenarios.

This structured breakdown provides a comprehensive understanding of the code's purpose, functionality, and underlying DAX principles. For further learning on DAX and its applications, consider exploring courses available on the Enterprise DNA platform.