问题
I\'d like to create a polar plot where the data is plotted in mathematical orientation (thus, the series starts and the east and continues counter-clockwise). The default behavior of JFreeChart\'s PolarPlot is to start north and continue the series clockwise.
Is there any support for this built in the PolarPlot class? I know how to transform the data to reach the goal, but this approach is rather cumbersome, since I\'d need to adapt the angle labeling too.
回答1:
As an aside, org.jfree.chart.plot.PolarPlot appears to have been designed for navigational and geodetic applications.
Using the transformation θ' = π/4 – θ and overriding refreshAngleTicks(), as suggested by @mort, produces reasonable results.
Addendum: See also this variation using the new 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);
}
}
回答2:
The current version of JFreeChart seems to solve this issue a lot easier:
There are three methods available:
setCounterClockwise(true) // changes the direction of the ticks
setAxisLocation(PolarAxisLocation.EAST_BELOW) // defines the placement of the axis
setAngleOffset(0);
Complete example adapted from 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);
}
}
回答3:
Unfortunately, there seems to be no built-in support for this. The angle labeling can be adapted by overriding the refreshAngleTicks() methods of PolarPlot:
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;
}
};
来源：https://stackoverflow.com/questions/3458824/jfreechart-polarplot-mathematical-orientation