How to Effectively Scale JFreeChart Boxplots with Multiple Categories?

Scaling JFreeChart Boxplots with Multiple Categories

Problem Statement:

While creating boxplots using JFreeChart for a CategoryDataset with numerous categories and series, it was noticed that the chart is not properly scaled. Either the subplot is too small or the legend and annotations are disproportionately large.

Proper Scaling Technique:

To ensure correct scaling, it is crucial to set the preferred size of the ChartPanel containing the chart, not the chart itself. This ensures that only the subplot is scaled while maintaining the size and readability of the legend and annotations.

Page-Based Approach:

In cases with an excessive number of categories, considering a page-based approach may be more practical. This involves dividing the data into smaller subsets and displaying only a portion of the data at a time. A control element, such as a scroll bar, can be added to navigate between the data pages.

Example:

The following code demonstrates a page-based implementation:

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.CategoryAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.renderer.category.BoxAndWhiskerRenderer;
import org.jfree.data.statistics.DefaultBoxAndWhiskerCategoryDataset;

public class BoxAndWhiskerDemo {

    private List<List<List<Double>>> data;
    private DefaultBoxAndWhiskerCategoryDataset dataset;
    private CategoryPlot plot;
    private ChartPanel chartPanel;
    private JPanel controlPanel;
    private int start = 0;
    private int visible = 4;

    public BoxAndWhiskerDemo() {
        createData();
        createDataset(start);
        createChartPanel();
        createControlPanel();
    }

    // Data generation and dataset creation
    // ...

    private void createChartPanel() {
        CategoryAxis xAxis = new CategoryAxis("Category");
        NumberAxis yAxis = new NumberAxis("Value");
        BoxAndWhiskerRenderer renderer = new BoxAndWhiskerRenderer();
        plot = new CategoryPlot(dataset, xAxis, yAxis, renderer);
        JFreeChart chart = new JFreeChart("BoxAndWhiskerDemo", plot);
        chartPanel = new ChartPanel(chart);
    }

    private void createControlPanel() {
        controlPanel = new JPanel();
        controlPanel.add(new JButton(new AbstractAction("\u22b2Prev") {
            @Override
            public void actionPerformed(ActionEvent e) {
                start -= visible;
                if (start < 0) {
                    start = 0;
                    return;
                }
                createDataset(start);
                plot.setDataset(dataset);
            }
        }));
        controlPanel.add(new JButton(new AbstractAction("Next\u22b3") {
            @Override
            public void actionPerformed(ActionEvent e) {
                start += visible;
                if (start >= data.size() - visible) {
                    start = data.size() - visible;
                    return;
                }
                createDataset(start);
                plot.setDataset(dataset);
            }
        }));
    }

    // ...

    public static void main(String[] args) {
        BoxAndWhiskerDemo demo = new BoxAndWhiskerDemo();
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(demo.getChartPanel(), BorderLayout.CENTER);
        frame.add(demo.getControlPanel(), BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
    }
}

This approach allows for a larger dataset to be displayed in a more manageable way while preserving the clarity of the chart elements.

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