Percentage Accuracy issue in JFreeChart Pie-chart

Question

I'm using Pie-chart of JFreeChart library for my need.
And i want to display percentage with total values in pie-chart. So, i searched over google. And i found this solution which is answered by @trashgod.

Now as per answer given by him i created class which is as following :

import java.awt.Color;
import java.awt.Dimension;
import java.text.DecimalFormat;

import javax.swing.JFrame;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.labels.PieSectionLabelGenerator;
import org.jfree.chart.labels.StandardPieSectionLabelGenerator;
import org.jfree.chart.plot.PiePlot;
import org.jfree.data.general.DefaultPieDataset;

public class TestPieChart {
    private static final String KEY1 = "Datum 1";
    public static final String KEY2 = "Datum 2";

    public static void main(String[] args) {
        DefaultPieDataset dataset = new DefaultPieDataset();
        dataset.setValue(KEY1, 45045); //49
        dataset.setValue(KEY2, 53955); //151

        JFreeChart someChart = ChartFactory.createPieChart(
            "Header", dataset, true, true, false);
        PiePlot plot = (PiePlot) someChart.getPlot();
        plot.setSectionPaint(KEY1, Color.green);
        plot.setSectionPaint(KEY2, Color.red);
        plot.setExplodePercent(KEY1, 0.10);
        plot.setSimpleLabels(true);

        PieSectionLabelGenerator gen = new StandardPieSectionLabelGenerator(
            "{0}: {1} ({2})", new DecimalFormat("0"), new DecimalFormat("0%"));
        plot.setLabelGenerator(gen);

        JFrame f = new JFrame("Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new ChartPanel(someChart) {
            @Override
            public Dimension getPreferredSize() {
                return new Dimension(400, 300);
            }
        });
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);

    }
}

What it gives output as follows:

In which percentage was 55% and 46%, Total is 101%
(Because it is taking upper limit for both values like 54.5 then 55)

But at the same time if i take value for KEY1 as 49 and KEY2 as 151, then it is giving accurate result as follows:
(Sum of both in this case is 100%)

So, My question is : Why JFreeChart is performing different for different values?
and is there any solution to fix this (total percentage will not cross 100) ?

score 2 · Accepted Answer · answered Sep 13 '18 at 16:42

The percentage calculation performed by the label generator's abstract parent, seen here, and the formatter's default rounding, discussed here, are both correct. If desired, you can change the precision of the displayed percentage by specifying a different percentFormat when constructing the StandardPieSectionLabelGenerator:

PieSectionLabelGenerator gen = new StandardPieSectionLabelGenerator(
    "{0}: {1} ({2})", new DecimalFormat("0"), new DecimalFormat("0.0%"));

Note that 45.5% + 54.5% = 100%.

Percentage Accuracy issue in JFreeChart Pie-chart

1 Answers1