Using JFreeChart to display recent changes in a time series

Question

How can I use JFreeChart to display just the most recent data in a continually updated time series?

Addenda: A complete, working example that incorporates the accepted answer is shown here. See also this variation having two series. See also this Q&A regarding setTimeBase().

Answer 1

The JFreeChart class DynamicTimeSeriesCollection is a good choice.

Addendum: As noted by @Bahadır, the last point of the series was persistently zero. @Don helpfully suggests advancing the time and then appending the data.

dataset.advanceTime(); dataset.appendData(newData); 

import java.awt.BorderLayout; import java.awt.EventQueue; import java.awt.FlowLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Random; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JPanel; import javax.swing.Timer; import org.jfree.chart.ChartFactory; import org.jfree.chart.ChartPanel; import org.jfree.chart.JFreeChart; import org.jfree.chart.axis.ValueAxis; import org.jfree.chart.plot.XYPlot; import org.jfree.data.time.DynamicTimeSeriesCollection; import org.jfree.data.time.Second; import org.jfree.data.xy.XYDataset; import org.jfree.chart.ui.ApplicationFrame; import org.jfree.chart.ui.UIUtils;  /**  * @see http://stackoverflow.com/a/15521956/230513  * @see http://stackoverflow.com/questions/5048852  */ public class DTSCTest extends ApplicationFrame {      private static final String TITLE = "Dynamic Series";     private static final String START = "Start";     private static final String STOP = "Stop";     private static final float MINMAX = 100;     private static final int COUNT = 2 * 60;     private static final int FAST = 100;     private static final int SLOW = FAST * 5;     private static final Random random = new Random();     private Timer timer;      public DTSCTest(final String title) {         super(title);         final DynamicTimeSeriesCollection dataset =             new DynamicTimeSeriesCollection(1, COUNT, new Second());         dataset.setTimeBase(new Second(0, 0, 0, 1, 1, 2011));         dataset.addSeries(gaussianData(), 0, "Gaussian data");         JFreeChart chart = createChart(dataset);          final JButton run = new JButton(STOP);         run.addActionListener(new ActionListener() {             @Override             public void actionPerformed(ActionEvent e) {                 String cmd = e.getActionCommand();                 if (STOP.equals(cmd)) {                     timer.stop();                     run.setText(START);                 } else {                     timer.start();                     run.setText(STOP);                 }             }         });          final JComboBox combo = new JComboBox();         combo.addItem("Fast");         combo.addItem("Slow");         combo.addActionListener(new ActionListener() {             @Override             public void actionPerformed(ActionEvent e) {                 if ("Fast".equals(combo.getSelectedItem())) {                     timer.setDelay(FAST);                 } else {                     timer.setDelay(SLOW);                 }             }         });          this.add(new ChartPanel(chart) {             @Override             public Dimension getPreferredSize() {                 return new Dimension(640, 480);             }         }, BorderLayout.CENTER);         JPanel btnPanel = new JPanel(new FlowLayout());         btnPanel.add(run);         btnPanel.add(combo);         this.add(btnPanel, BorderLayout.SOUTH);          timer = new Timer(FAST, new ActionListener() {             float[] newData = new float[1];              @Override             public void actionPerformed(ActionEvent e) {                 newData[0] = randomValue();                 dataset.advanceTime();                 dataset.appendData(newData);             }         });     }      private float randomValue() {         return (float) (random.nextGaussian() * MINMAX / 3);     }      private float[] gaussianData() {         float[] a = new float[COUNT];         for (int i = 0; i < a.length; i++) {             a[i] = randomValue();         }         return a;     }      private JFreeChart createChart(final XYDataset dataset) {         final JFreeChart result = ChartFactory.createTimeSeriesChart(             TITLE, "hh:mm:ss", "milliVolts", dataset, true, true, false);         final XYPlot plot = result.getXYPlot();         ValueAxis domain = plot.getDomainAxis();         domain.setAutoRange(true);         ValueAxis range = plot.getRangeAxis();         range.setRange(-MINMAX, MINMAX);         return result;     }      public void start() {         timer.start();     }      public static void main(final String[] args) {         EventQueue.invokeLater(new Runnable() {             @Override             public void run() {                 DTSCTest demo = new DTSCTest(TITLE);                 demo.pack();                 UIUtils.centerFrameOnScreen(demo);                 demo.setVisible(true);                 demo.start();             }         });     } } 

Answer 2

You can also eliminate the zero by first advanceTime(), then appendData. (swap the way they are doing it in the example).