How do select last five weeks in matrix and display auto append

Following these steps may resolve your query-

1) Select the matrix/visualization from the canvas
2) Go to the filters pane 
3) Go to 'Filters on the visual' > Drag your column field and then expand it
4) From filter type select 'Top N'
5) Beside top enter value as 5
6) Drag your column field again in 'By Value' and click apply filter

This may resolve your query of showing the last five weeks and it will also do auto append to show the latest week as soon as the data is updated

Anonymous , check suggestion by Anonymous ,

You can create a new column like this in date table, and select last 5 week and save

Week Type =
var _st = today() +-1*WEEKDAY(today() ,2)+1 -35
var _end = today() + 7-1*WEEKDAY(today(),2)
return
Switch( True(),
[Date] >= _st && [Date] <= _end ,"Last 5 week" ,
[Week Name]
)

thank you