Charting a count of records returned

I am trying to create some charts in Flex/FlashBuilder 4.5

The issue I have it that the information I wish to display is the number of events within an area. I am using HTTP service to acce开发者_JAVA百科ss a rails controller which is returning an XML list of the events.

I need to figure out how to chart the number of events, eg number of records returned. There is no numeric value within chart, as there would be if I was charting sales or prices for example.

I'm a little stumped as to the best way to do this?

Use a dataFunction. Check out http://flexdiary.blogspot.com/2008/08/charting-example.html for an example that uses one.