Hi, I'd like to use this example of grouped bar chart :

http://dev.sencha.com/deploy/ext-4.0.0/examples/charts/GroupedBar.html

but I'd like to inverse the axis fields, instead of the horizontal bars, I want them vertical, how do I do that?
I tried reversing positions or xField and yField values but the result is not what I want.
Please any help would be very much appreciated, since I'm only beginning in Extjs.

Thanks