In the example we're looking at historical weather data for New York provided by intellicast.com and wunderground.com. Inspired by weather-radicals.com.
This example uses scales to roll your own radial projection by mapping out the x, y, and r positions. If you are creating a line or an area you can use d3's convenience functions d3.svg.line.radial and d3.svg.area.radial but this is a method you can use if you want to use different graphical elements in a circular layout.