A radial chart of USA airlines on-time performance.

Things have done:

• Used a cleaner way to transform the chart to center
• Learned how to close the line: using d3.curveLinearClosed
• Used a cleaner way to choose the range for radiusScale: innerRadius, outerRadius, angleAxisOffset
• Added a colorLegend

Things doing:

• Adding axes (tick marks and labels) for angle: using pointRadial
• Making the colorLegend interactive

Things to do:

• Adding axes (tick marks and labels) for radius
• Choosing a range for the angle scale that represents some periodic amount of time, like years, months, or weeks.