Minor ticks not showing up on LogAxis in JFreeChart

Question

I\'m using JFreeChart to plot some data and using a LogAxis for the range axis. I\'m stumped as to why I can\'t seem to get the minor ticks to show up

Answer 1

LogAxis supports minor ticks for gridlines, as your fragment shows. In contrast LogarithmicAxis allows full customization of tick marks, as shown below. The color and stroke of the tick marks have been exaggerated for emphasis.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.BasicStroke;
import java.text.NumberFormat;
import javax.swing.JFrame;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.LogarithmicAxis;
import org.jfree.chart.axis.NumberTickUnit;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

//** @see https://stackoverflow.com/a/54097313/230513 */
public class ChartOne {

    public static ChartPanel createChart() {

        XYSeriesCollection dataset = new XYSeriesCollection();
        XYSeries x1 = new XYSeries("Series 1");
        x1.add(0.5, 2);
        x1.add(1, 2.2);
        x1.add(2, 2.4);
        x1.add(10, 2.75);
        x1.add(30, 4);
        x1.add(120, 7);
        dataset.addSeries(x1);
        XYSeries x2 = new XYSeries("Series 2");
        x2.add(0.5, 6);
        x2.add(1, 7);
        x2.add(2, 8);
        x2.add(10, 14);
        x2.add(30, 18);
        x2.add(120, 22);
        dataset.addSeries(x2);

        JFreeChart chart = ChartFactory.createXYLineChart(
            "Data", "Exposure", "Percentage uptake", dataset,
            PlotOrientation.VERTICAL, false,  true, false);

        LogarithmicAxis xAxis = new LogarithmicAxis("Time");
        xAxis.setTickUnit(new NumberTickUnit(1.0, NumberFormat.getInstance(), 9));
                xAxis.setTickMarkInsideLength(2f);
                xAxis.setTickMarkOutsideLength(4f);
                xAxis.setTickMarkPaint(Color.GREEN);
                xAxis.setTickMarkStroke(new BasicStroke(2f));
        xAxis.setMinorTickMarksVisible(true);

        XYPlot plot = (XYPlot) chart.getPlot();
        plot.setDomainAxis(xAxis);
        plot.setDomainMinorGridlinesVisible(true);
        plot.setDomainGridlinePaint(Color.BLACK);
        plot.setDomainMinorGridlinePaint(Color.BLACK);
        plot.setBackgroundPaint(Color.WHITE);
        return new ChartPanel(chart){
            @Override
            public Dimension getPreferredSize() {
                return new Dimension(600, 400);
            }
        };
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            JFrame frame = new JFrame("Chart");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(createChart(), BorderLayout.CENTER);
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }
}