ISBLANK Function (DAX)
Checks whether a value is blank, and returns TRUE or FALSE.
This formula computes the increase or decrease ratio in sales compared to the previous year. The example uses the IF function to check the value for the previous year's sales in order to avoid a divide by zero error.
Total Sales Previous Year
Sales to Previous Year Ratio
//Sales to Previous Year Ratio =IF( ISBLANK('CalculatedMeasures'[PreviousYearTotalSales]) , BLANK() , ( 'CalculatedMeasures'[Total Sales]-'CalculatedMeasures'[PreviousYearTotalSales] ) /'CalculatedMeasures'[PreviousYearTotalSales])