使用 JFreeChart 为两个系列设置不同的 y 轴

Question

我正在使用 JFreeChart 使用折线图绘制两个系列的数据 (XYSeries)。 复杂的因素是其中一个数据系列的 y 值通常远高于我的第二个数据系列的 y 值（假设第一个系列的 y 值在数百万数量级，而第二个系列的 y 值在数百个数量级）。我的第一个数据集中存在高值会导致绘图范围如此之大，以至于我的第二个数据集的 y 值不再可理解。

在绘图中添加第二个 y 轴，这样我的两个数据系列都使用自己的 y 轴，可以解决这个问题。有谁知道如何使用 JFreeChart 做到这一点？

完整性的当前代码：

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

您可以手动创建 JFreeChart 对象，而不是使用 ChartFactory。首先生成数据集和绘图，将每个数据集设置为索引。然后您可以使用必要的轴和渲染器自定义绘图。这是一个使用具有两个数据集的虚拟数据执行此操作的示例，每个数据集具有不同的幅度 y 值：

    //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

我已调整上述解决方案以使用最新版本的 JFreeChart（2019 年 1 月 29 日）。

如果正确导入 JFreeChart 库，这将正确运行。我有一个pom.xml 像这样使用导入设置

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

这里是完整的sn-p代码：

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);
    }