This is what it looks like in its initial state:
The smaller graph below acts as a range control for the large (display) graph above. When you select a range for example from January 2001 - January 2002, the large graph will update to show only data within that range.
The problem I have with this interface that the relationship of the two graphs is very unclear for first time users.
My question is:
How have other people solved problems like this? Are there any established design patterns for problems like this?