JFreeChart PolarPlot：数学方向

Question

我想创建一个极坐标图，其中数据以数学方向绘制（因此，系列开始，向东并逆时针继续）。 JFreeChart的PolarPlot的默认行为是从北方开始并顺时针继续该系列。

在PolarPlot课程中是否有任何支持？我知道如何转换数据以达到目标，但这种方法相当麻烦，因为我也需要调整角度标注。

Answer 1

另外，org.jfree.chart.plot.PolarPlot似乎是designed和navigational应用的geodetic。

使用变换θ'=π/ 4-θ并覆盖refreshAngleTicks()，由@mort作为suggested，产生合理的结果。

附录：请参阅此variation使用新的PolarPlot API。

import java.awt.Color;
import java.awt.Dimension;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.axis.NumberTick;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.chart.plot.PolarPlot;
import org.jfree.chart.renderer.DefaultPolarItemRenderer;
import org.jfree.chart.renderer.PolarItemRenderer;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;
import org.jfree.ui.TextAnchor;

/**
 * @see http://en.wikipedia.org/wiki/Polar_coordinate_system
 * @see https://stackoverflow.com/questions/3458824
 */
public class ArchimedesSpiral extends JFrame {

    private static final String title = "Archimedes' Spiral";

    public ArchimedesSpiral(String title) {
        super(title);
        JFreeChart chart = createChart(createDataset());
        ChartPanel panel = new ChartPanel(chart);
        panel.setPreferredSize(new Dimension(500, 500));
        panel.setMouseZoomable(false);
        this.add(panel);
    }

    private static XYDataset createDataset() {
        XYSeriesCollection result = new XYSeriesCollection();
        XYSeries series = new XYSeries(title);
        for (int t = 0; t <= 3 * 360; t++) {
            series.add(90 - t, t);
        }
        result.addSeries(series);
        return result;
    }

    private static JFreeChart createChart(XYDataset dataset) {
        ValueAxis radiusAxis = new NumberAxis();
        radiusAxis.setTickLabelsVisible(false);
        PolarItemRenderer renderer = new DefaultPolarItemRenderer();
        PolarPlot plot = new PolarPlot(dataset, radiusAxis, renderer) {

            @Override
            protected List refreshAngleTicks() {
                List<NumberTick> ticks = new ArrayList<NumberTick>();
                int delta = (int) this.getAngleTickUnit().getSize();
                for (int t = 0; t < 360; t += delta) {
                    int tp = (360 + 90 - t) % 360;
                    NumberTick tick = new NumberTick(
                        Double.valueOf(t), String.valueOf(tp),
                        TextAnchor.CENTER, TextAnchor.CENTER, 0.0);
                    ticks.add(tick);
                }
                return ticks;
            }
        };
        plot.setBackgroundPaint(new Color(0x00f0f0f0));
        plot.setRadiusGridlinePaint(Color.gray);
        plot.addCornerTextItem("r(θ) = θ; 0 < θ < 6π");
        JFreeChart chart = new JFreeChart(
            title, JFreeChart.DEFAULT_TITLE_FONT, plot, true);
        chart.setBackgroundPaint(Color.white);
        return chart;
    }

    public static void main(String[] args) {
        ArchimedesSpiral demo = new ArchimedesSpiral(title);
        demo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        demo.pack();
        demo.setLocationRelativeTo(null);
        demo.setVisible(true);
    }
}

Answer 2

当前版本的JFreeChart似乎更容易解决这个问题：有三种方法可用：

setCounterClockwise(true) // changes the direction of the ticks
setAxisLocation(PolarAxisLocation.EAST_BELOW) // defines the placement of the axis
setAngleOffset(0);

完整的例子改编自here：

import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.chart.plot.PolarAxisLocation;
import org.jfree.chart.plot.PolarPlot;
import org.jfree.chart.renderer.DefaultPolarItemRenderer;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see http://en.wikipedia.org/wiki/Polar_coordinate_system
 * @see https://stackoverflow.com/questions/3458824
 * @see https://stackoverflow.com/questions/6540390
 * @see https://stackoverflow.com/questions/6576911
 * @see https://stackoverflow.com/a/10227275/230513
 */
public class ArchimedesSpiral extends JFrame {

    private static final String title = "Archimedes' Spiral";

    public ArchimedesSpiral(String title) {
        super(title);
        JFreeChart chart = createChart(createDataset());
        ChartPanel panel = new ChartPanel(chart);
        panel.setPreferredSize(new Dimension(500, 500));
        panel.setMouseZoomable(false);
        this.add(panel);
    }

    private static XYDataset createDataset() {
        XYSeriesCollection result = new XYSeriesCollection();
        XYSeries series = new XYSeries(title);
        for (int t = 0; t <= 3 * 360; t++) {
            series.add(t, t);
        }
        result.addSeries(series);
        return result;
    }

    private static JFreeChart createChart(XYDataset dataset) {
        ValueAxis radiusAxis = new NumberAxis();
        radiusAxis.setTickLabelsVisible(false);
        DefaultPolarItemRenderer renderer = new DefaultPolarItemRenderer();
        renderer.setShapesVisible(false);
        PolarPlot plot = new PolarPlot(dataset, radiusAxis, renderer);
        plot.setCounterClockwise(true);
        plot.setAxisLocation(PolarAxisLocation.EAST_BELOW);
        plot.setAngleOffset(0);
        plot.setBackgroundPaint(new Color(0x00f0f0f0));
        plot.setRadiusGridlinePaint(Color.gray);
        plot.addCornerTextItem("r(θ) = θ; 0 < θ < 6π");
        JFreeChart chart = new JFreeChart(
            title, JFreeChart.DEFAULT_TITLE_FONT, plot, true);
        chart.setBackgroundPaint(Color.white);
        return chart;
    }

    public static void main(String[] args) {
        ArchimedesSpiral demo = new ArchimedesSpiral(title);
        demo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        demo.pack();
        demo.setLocationRelativeTo(null);
        demo.setVisible(true);
    }
}

Answer 3

不幸的是，似乎没有内置的支持。可以通过覆盖PolarPlot的refreshAngleTicks（）方法来调整角度标注：

PolarPlot plot = new PolarPlot() {

        @Override
        protected List refreshAngleTicks() {
            List ticks = new ArrayList();
            // produce some ticks, e.g. NumberTick instances
            ticks.add(new NumberTick(0, "90", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(45, "45", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(90, "0", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(135, "315", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(180, "270", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(225, "225", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(270, "180", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            ticks.add(new NumberTick(315, "135", TextAnchor.TOP_LEFT, TextAnchor.TOP_LEFT, 0));
            return ticks;
        }
    };