The MAT curve helps in smoothing out the spikes that occur in a single month by making use of the annual totals. This is achieved by calculating the rolling 12 months accumulated sales data for each data point. We create a MAT MonthYear field. You will notice that when we select any month and year value in this field, it associates the field value with the current MonthYear, and the 11 MonthYears prior to the current, in the MonthYear field. In the MAT Sales expression, we make sure that the rolling 12 months are always shown in the chart. This is achieved by restricting the MAT MonthYear values shown in the chart between the vRolling12Months and the vMaxMonth variables. Selecting any MAT MonthYear will result in the trendline chart populating the MAT figures for the selected month and 11 months prior to that.