Set 'focus' area in nvd3.js lineWithFocusChart-open source projects novus/nvd3

I’m usuing the lineWithFocusChart.js model shown in the nvd3 examples shown here: http://nvd3.org/ghpages/examples.html

I want to be able to choose a specific x range for the graph to be focused on at load. I thought there would be a variable in chart that I could set to accomplish this.