JFreechart draw an arc on a chart

Question

I have 2 questions

1) I am trying to draw an arc on XYplot using form annotation. I used the XYLine annotation to draw a line, and I want the arc to start where the line ends. I am having some problems with the parameters. I want the arc to have a height of 17, a width of 44, and start at the point (3.0, 17) of the graph (the line ends here). But the code below does not work. Can someone please tell me what is wrong with the code?

Arc2D.Double arc = new Arc2D.Double(3.0, 16.9, 44.0, 17.04, 180.0, 180.0, Arc2D.OPEN ); plot.addAnnotation(new XYShapeAnnotation(arc, new BasicStroke(2.0f), Color.white)); XYLineAnnotation a1 = new XYLineAnnotation(3.0, 0.0, 3.0, 16.9, new BasicStroke(2.0f), Color.white); 

2) How can I draw a similar figure on a polar plot?

thanks

Answer 1

• The critical thing about Arc2D is the bounding box. To make half an arc of H units high, the borders should be 2 * H units high.

• AFAIK, PolarPlot does not support annotations.

 import java.awt.BasicStroke; import java.awt.Color; import java.awt.geom.Arc2D; import java.util.Random; import org.jfree.chart.ChartFactory; import org.jfree.chart.ChartFrame; import org.jfree.chart.JFreeChart; import org.jfree.chart.annotations.XYLineAnnotation; import org.jfree.chart.annotations.XYShapeAnnotation; import org.jfree.chart.plot.PlotOrientation; import org.jfree.chart.plot.XYPlot; import org.jfree.data.xy.XYDataset; import org.jfree.data.xy.XYSeries; import org.jfree.data.xy.XYSeriesCollection; /** @see http://stackoverflow.com/questions/6604211 */ public class ArcTest { private static final Random r = new Random(); private static final double PI = 180d; private static final int X = 3; private static final int Y = 0; private static final int W = 44; private static final int H = 17; public static void main(String[] args) { JFreeChart chart = ChartFactory.createXYLineChart( "ArcTest", "X", "Y", createDataset(), PlotOrientation.VERTICAL, true, true, false); XYPlot plot = chart.getXYPlot(); XYLineAnnotation line = new XYLineAnnotation( X, Y, X, H, new BasicStroke(2f), Color.blue); plot.addAnnotation(line); Arc2D.Double arc = new Arc2D.Double( X, Y, W, 2 * H, PI, PI, Arc2D.OPEN); plot.addAnnotation(new XYShapeAnnotation(arc, new BasicStroke(2.0f), Color.blue)); ChartFrame frame = new ChartFrame("First", chart); frame.pack(); frame.setVisible(true); } private static XYDataset createDataset() { XYSeriesCollection result = new XYSeriesCollection(); XYSeries series = new XYSeries("ArcTest"); series.add(0, 0); series.add(W, W); result.addSeries(series); return result; } }