JFreeChart's Bar Chart Bar Unit

Question

I\'m trying to create a bar chart in Java.

I\'d like to have 1H bar unit on the DateAxis (not tick unit). Is there a way? After a lot of google search,

Answer 1

I've simplified your example to focus on the intervals comprising the dataset. Using intervals of one Calendar.HOUR ensures that the bars appear one hour wide. Although your question specifically eschews tick units, some features may be useful going forward:

• Use the approach shown here to get a specific tick interval.

  domainAxis.setTickUnit(new DateTickUnit(DateTickUnitType.HOUR, 1));
  

• Use setTickMarkPosition() to center the tick marks in the chosen interval.

  domainAxis.setTickMarkPosition(DateTickMarkPosition.MIDDLE);
  

import java.awt.EventQueue;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Random;
import javax.swing.JFrame;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.DateTickMarkPosition;
import org.jfree.chart.axis.DateTickUnit;
import org.jfree.chart.axis.DateTickUnitType;
import org.jfree.chart.labels.StandardXYToolTipGenerator;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYItemRenderer;
import org.jfree.data.time.Hour;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.IntervalXYDataset;

/** @see https://stackoverflow.com/a/42612723/230513 */
public class Test {

    public static void main(String[] args) {

        EventQueue.invokeLater(() -> {
            Test frame = new Test();
        });
    }

    public Test() {
        JFrame f = new JFrame("Data");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new ChartAdapter().generateChart("Data"));
        f.pack();
        f.setVisible(true);
    }

    class ChartAdapter {

        public ChartPanel generateChart(String title) {
            JFreeChart chart = ChartFactory.createXYBarChart(
                title, "Time", true, "Value", createDataset(),
                PlotOrientation.VERTICAL, true, false, false
            );
            final XYItemRenderer renderer = chart.getXYPlot().getRenderer();
            final StandardXYToolTipGenerator generator = new StandardXYToolTipGenerator(
                "{1} : {2}", new SimpleDateFormat("HH:mm"), new DecimalFormat("0.00")
            );
            renderer.setBaseToolTipGenerator(generator);
            final XYPlot plot = chart.getXYPlot();
            final DateAxis domainAxis = (DateAxis) plot.getDomainAxis();
            domainAxis.setVerticalTickLabels(true);
            domainAxis.setTickUnit(new DateTickUnit(DateTickUnitType.HOUR, 1));
            domainAxis.setTickMarkPosition(DateTickMarkPosition.MIDDLE);
            domainAxis.setDateFormatOverride(new SimpleDateFormat("HH:mm"));
            return new ChartPanel(chart);
        }

        private IntervalXYDataset createDataset() {
            Random r = new Random();
            TimeSeries series = new TimeSeries("Value");
            Calendar c = Calendar.getInstance();
            for (int i = 0; i < 10; i++) {
                series.add(new Hour(c.getTime()), r.nextGaussian() + 7);
                c.add(Calendar.HOUR, 1);
            }
            return new TimeSeriesCollection(series);
        }
    }
}