autoscaling y-axis after changing xmin and xmax?

I'm using matplotlib 0.87.5. I'm working on an application that has an interface that allows the user to change xmin and xmax to focus in on portions of the dataset. I'd like the y axis to autoscale each time the xmin and/or xmax are changed. I've confirmed that autoscale_on is True, but no autoscaling occurs.

What drives the y axis autoscaling? Does it look only at the data between xmin and xmax, or does it look at the whole data series? Is there a way to make autoscale do what I want, or would I need to change the data set each time to only be plotting between xmin and xmax?

Kevin Horton
Ottawa, Canada