You can export an indivdual form view to Excel, but I do not think that is what you want.
You want to be able to graph responses from all docuemnts.
This is typical in a feedback survey or where ratings are collected.
You need the ability to export your data to a database from each form, then you can use Excel or SQL web reports to create a graph or report. With SQL Reporting Services you can have a real-time graph of your live data as it is submitted. This beats having to update a spreadsheet manually all the time.