Hi Naveen, thanks so much for your reply, but I'd like to ask: so I have to create 2 different workbooks each for overall and each region? and also why Region should be added to context?
No different Sheets its in single sheet
The reason why region is context because Top filter and dimension filter wont go along
Check the order of operations in Tableau
Here is simple solution to your problem
1) Create Parameter as Region and add All value extra
2)Write this calculation
WHEN 'South' THEN [Region]='South'
WHEN 'East' THEN [Region]='East'
WHEN 'Central' THEN [Region]='Central'
WHEN 'West' THEN [Region]='West'
WHEN 'All' THEN ([Region]='South' OR [Region]='East'
OR [Region]='Central' OR [Region]='West'
drag to filter shelf and select True.
Now the output will be according to regions and 'All' will select data for all region.
Let me know if it works.