I implemented a chart.
chart name is sales by country.(dimension->country, expression->sum(sales))
after that i changed dimension as state.then i want sales by state. without changing chart name?
write a condition in title it will change chart name based on selections
You can use getfieldselection() function to identify which mode is active each time and then use an if condition to change the chart tile accordingly.
Are you using a cycle group to switch dimensions ? If you are you can use the function getcurrentfield( myGroup ) to do this. You may need to put the group name in square brackets 
Can u upload the attachment?
Here is one:
Retrieving data ...