Generating XML

Hello!
I'm trying to show some simple data, and I'm not yet sure if I need to have a real XML file to be passed to the

module_invoke('swfcharts', 'chart', $data);

function. I tried passing an array ($data is an array, well formed as in many examples), but the graph is always the demo one. 3 Years, Region A, region B...
I'm wondering if I need to create an xml file from that array and then pass it to the function.

Any help would be appreciated!

Thanks