Moving Average

Hello all,

I'm new to Power BI and have a query on some data analysis I'd like to perform. Any help would be much appreciated:

I have a table of sales data which details sales at item level. Two of the columns are 'date' and 'item category'. My objective if to identify when particular customers aren't buying a particluar item category by identifying the moving average of monthly sales by category, and looking at customers whose current month's sales (by category) are below this moving average.

Acheiving this resutl in excel required creating a pivot table so summarise sales per month and then calculating a moving average of the resuls. I'm unsure how I would go about this in Power BI desktop.

Thanks,

Oliver