Calculating average for the Previous 6 weeks.

Anonymous , Make sure you  have a separate week/date table

Have these new columns in Date Table, Week Rank is Important in Date/Week Table

Week Rank = RANKX('Date','Date'[Week Start date],,ASC,Dense)
OR
Week Rank = RANKX('Date','Date'[Year Week],,ASC,Dense) //YYYYWW format

Avg Last 6 weeks = CALCULATE(Averagex(Values('Date'[Week Rank]), [Your Measure]) , FILTER(ALL('Date'),'Date'[Week Rank]>=max('Date'[Week Rank])-5 && 'Date'[Week Rank]<=max('Date'[Week Rank])))

or

Avg Last 6 weeks = CALCULATE(Averagex(Values('Date'[Week Rank]), [Your Measure]) , FILTER(ALL('Date'),'Date'[Week Rank]>=max('Date'[Week Rank])-6 && 'Date'[Week Rank]<=max('Date'[Week Rank])))

Power BI — Week on Week and WTD
https://medium.com/@amitchandak.1978/power-bi-wtd-questions-time-intelligence-4-5-98c30fab69d3
https://community.powerbi.com/t5/Community-Blog/Week-Is-Not-So-Weak-WTD-Last-WTD-and-This-Week-vs-Last-Week/ba-p/1051123
https://www.youtube.com/watch?v=pnAesWxYgJ8
Time Intelligence, Part of learn Power BI https://youtu.be/cN8AO3_vmlY?t=27510