If I understood you right, you want the last 6 month bzw. 6 weeks to be displayed.
First: how do you detect if you want to see weeks or months?
To the solution:
- Switch off any dimension limits
- In the Presentation tab, activate 'Enable X-Axis Scrollbar'
- Set 'When Number of Items Exceeds' to 6 (or whatever suits you)
- activate 'Reversed' so it will take the 6 last values
Should now display the last 6 months/ weeks only, just as you wish.
I guess with that solution you can use simple expressions
Hope that did help!
P.S. See the attached file where I did what I wrote above
solution.qvw 168.8 K