java - Multiple axes on the same data

Question

I'm trying to have two axes on the same data.

The data is a couple of DefaultTableXYDatasets. The plot is a XYPlot, and I have two XYLineAndShapeRenderers and one StackedXYAreaRenderer2.

All data is in meters for the y-values, and I want to have one axis displaying it in meters and one axis displaying it in feet. Now this feels like a common thing to do, but I can't decide on the most obvious way to do it. One way that works would be to duplicate the data and have the y-values in feet, then add another NumberAxis and be done with it.

But I thought it would be wiser to subclass NumberAxis, or inject some functionality into NumberAxis to scale the values. Or should I go with the first approach?

What do you think?

Answer 1

Eventually i settled on this solution, it might not be the most elegant but it worked. I have a second axis feetAxis, and added a AxisChangeListener on the first axis called meterAxis. When the meterAxis changes set the range on feetAxis.

I used SwingUtilities.invokeLater, otherwise the range would be incorrect when zooming out of the chart, then the feetAxis would only go from 0 to 1. Didn't check why though.

feetAxis = new NumberAxis("Height [ft]");
metersAxis = new NumberAxis("Height [m]");
pathPlot.setRangeAxis(0, metersAxis);
pathPlot.setRangeAxis(1, feetAxis);

metersAxis.addChangeListener(new AxisChangeListener() {

   @Override
   public void axisChanged(AxisChangeEvent event) {

       SwingUtilities.invokeLater(new Runnable() {

           @Override
           public void run() {
               feetAxis.setRange(metersAxis.getLowerBound() * MetersToFeet, metersAxis.getUpperBound() * MetersToFeet);
                }
           });
       }
   });