Question

I am using the JFreeChart API to generate some chart in my Java application. In one of my charts, I try to use the LogAxis object to make my y-axis a log-scale axis (A in the figure) by the following code:

LogAxis logAxis = new LogAxis("Price($)");
logAxis.setMinorTickMarksVisible(true);
logAxis.setAutoRange(true);
xyplot.setRangeAxis(logAxis);

Then I got a y-axis in log-scale with ticks like 10^n (like figure A). I want to make it like B, which is more intuitive to the user, and each interval represents different values, as shown in the figure, 2->4, 4->8, 8->16, the interval grows as 2^n. Something minor is that, the intervals are displaying equally wide even if they are representing different value. However, when O try to achieve this by the following code :

LogAxis logAxis = new LogAxis("Price($)");
logAxis.setBase(2);
logAxis.setTickUnit(new NumberTickUnit(2));
logAxis.setMinorTickMarksVisible(true);
logAxis.setAutoRange(true);
xyplot.setRangeAxis(logAxis);

What I get is something like figure C.

How can I achieve figure B?

Answer 1

Even though you’re using a LogAxis, you can specify integer tick units, as shown in the variation of @amaidment’s example below.

/** @see http://stackoverflow.com/a/10353270/230513 */
private static void createFrame() {
    XYSeries series = new XYSeries("Series");
    for (int i = 0; i <= N; i++) {
        series.add(i, Math.pow(2, i));
    }
    NumberAxis xAxis = new NumberAxis("X");
    xAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());
    LogAxis yAxis = new LogAxis("Y");
    yAxis.setBase(2);
    yAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());
    XYPlot plot = new XYPlot(new XYSeriesCollection(series),
        xAxis, yAxis, new XYLineAndShapeRenderer(true, false));
    JFreeChart chart = new JFreeChart(
        "Chart", JFreeChart.DEFAULT_TITLE_FONT, plot, false);
    JFrame frame = new JFrame("LogAxis Test");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(new ChartPanel(chart));
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {

        @Override
        public void run() {
            createFrame();
        }
    });
}