Setting different y-axis for two series with JFreeChart

Question

I am using JFreeChart to plot two series of data (XYSeries) using a linechart. The complicating factor is that one of the data series has y-values that are typically much higher than the y-values of my second data series (let's say that the first series has y-values in the order of magnitude of millions, while the second series has y-values in the order of magnitude of hundreds). The existence of the high values in my first data set cause the range of the plot to be such that the y-values of my second data set are not comprehensible anymore.

Adding a second y-axis to the plot, such that both my data series use their own y-axis, would solve this problem. Does anyone know how to do this with JFreeChart?

Current code for completeness:

XYSeriesCollection dataset = new XYSeriesCollection();
XYSeries series1 = new XYSeries("series1");
XYSeries series2 = new XYSeries("series2");

// Here is my code to fill series1 and series2 with data    

dataset.addSeries(series1);
dataset.addSeries(series2);

JFreeChart chart = ChartFactory.createXYLineChart(
    "title", "x-axis title", "y-axis title", dataset, PlotOrientation.VERTICAL, true, true, false
);
chart.getXYPlot().setRenderer(new XYSplineRenderer());

Answer 1

You can manually create the JFreeChart object instead of using ChartFactory. First generate the datasets and Plot, setting each dataset to an index. Then you can customize the Plot with the necessary Axis and Renderer. Here's an example for doing so with dummy data that has two datasets, each with different magnitude y-values:

    //create the series - add some dummy data
    XYSeries series1 = new XYSeries("series1");
    XYSeries series2 = new XYSeries("series2");
    series1.add(1000, 1000);
    series1.add(1150, 1150);
    series1.add(1250, 1250);

    series2.add(1000, 111250);
    series2.add(1150, 211250);
    series2.add(1250, 311250);

    //create the datasets
    XYSeriesCollection dataset1 = new XYSeriesCollection();
    XYSeriesCollection dataset2 = new XYSeriesCollection();
    dataset1.addSeries(series1);
    dataset2.addSeries(series2);

    //construct the plot
    XYPlot plot = new XYPlot();
    plot.setDataset(0, dataset1);
    plot.setDataset(1, dataset2);

    //customize the plot with renderers and axis
    plot.setRenderer(0, new XYSplineRenderer());//use default fill paint for first series
    XYSplineRenderer splinerenderer = new XYSplineRenderer();
    splinerenderer.setSeriesFillPaint(0, Color.BLUE);
    plot.setRenderer(1, splinerenderer);
    plot.setRangeAxis(0, new NumberAxis("Series 1"));
    plot.setRangeAxis(1, new NumberAxis("Series 2"));
    plot.setDomainAxis(new NumberAxis("X Axis"));

    //Map the data to the appropriate axis
    plot.mapDatasetToRangeAxis(0, 0);
    plot.mapDatasetToRangeAxis(1, 1);   

    //generate the chart
    JFreeChart chart = new JFreeChart("MyPlot", getFont(), plot, true);
    chart.setBackgroundPaint(Color.WHITE);
    JPanel chartPanel = new ChartPanel(chart);

Answer 2

I have adapted the solution above to work with the newest version of JFreeChart (2019-Jan-29).

This will run correctly if the JFreeChart library is imported correctly. I have a pom.xml set up with the import like so

 <dependency>
        <groupId>org.jfree</groupId>
        <artifactId>jfreechart</artifactId>
        <version>1.0.19</version>
 </dependency>

Here is the full code snippet:

import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYSplineRenderer;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

import javax.swing.*;
import java.awt.*;

class GraphTest2 {
    // driver that actually runs the thing
    public static void main(String[] args) {
        SwingUtilities.invokeLater( () -> {
            LineChartEx ex = new LineChartEx();
            ex.setVisible(true);
        });
    }
}

class LineChartEx extends JFrame {
    public LineChartEx() {
        initUI();
    }

    private void initUI() {
        //create the series - add some dummy data
        XYSeries series1 = new XYSeries("series1");
        XYSeries series2 = new XYSeries("series2");
        series1.add(1000, 1000);
        series1.add(1150, 1150);
        series1.add(1250, 1250);

        series2.add(1000, 111250);
        series2.add(1150, 211250);
        series2.add(1250, 311250);

        //create the datasets
        XYSeriesCollection dataset1 = new XYSeriesCollection();
        XYSeriesCollection dataset2 = new XYSeriesCollection();
        dataset1.addSeries(series1);
        dataset2.addSeries(series2);

        //construct the plot
        XYPlot plot = new XYPlot();
        plot.setDataset(0, dataset1);
        plot.setDataset(1, dataset2);

        //customize the plot with renderers and axis
        plot.setRenderer(0, new XYSplineRenderer());//use default fill paint for first series
        XYSplineRenderer splinerenderer = new XYSplineRenderer();
        splinerenderer.setSeriesFillPaint(0, Color.BLUE);
        plot.setRenderer(1, splinerenderer);
        plot.setRangeAxis(0, new NumberAxis("Series 1"));
        plot.setRangeAxis(1, new NumberAxis("Series 2"));
        plot.setDomainAxis(new NumberAxis("X Axis"));

        //Map the data to the appropriate axis
        plot.mapDatasetToRangeAxis(0, 0);
        plot.mapDatasetToRangeAxis(1, 1);

        //generate the chart
        JFreeChart chart = new JFreeChart("MyPlot", getFont(), plot, true);
        chart.setBackgroundPaint(Color.WHITE);
        //JPanel jpanel = new ChartPanel(chart);


        // NEW PART THAT MAKES IT WORK
        ChartPanel chartPanel = new ChartPanel(chart);
        chartPanel.setBorder(BorderFactory.createEmptyBorder(15, 15, 15, 15));
        chartPanel.setBackground(Color.white);
        add(chartPanel);

        pack();
        setTitle("Line chart");
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }