On Adding a Start Value to a Waterfall Chart in Power BI

Waterfall charts in Power BI natively lack the ability to include a starting value, such as a prior year's total, before showing incremental changes. A solution to this problem involves expanding the data model by adding a second, independent date table to handle report selections. This modified structure enables the creation of a complex DAX measure that calculates the year-end value from the previous period to serve as the chart's starting point. The final measure uses a SWITCH function to conditionally return either this initial total or the monthly values for the selected year, achieving the desired visualization.