CODEWITHSUNDEEP
javahistogramjfreechart
Jakub Peschel
Jakub Peschel

Reputation: 135

How to set JFreeChart.Histogram to corespond to data

I am trying to show a histogram of lengths of Lists in my data. I decided to use JFreeCharts to visualise it, but I fit the data into tool and histogram that is created doesn't correspond to that data.

At first, I tried to set corresponding labels to x-axes. Unfortunately, I was able to only set the correct start (1) and end (dataAray.length). But even with that, I feel it is not the correct way. I would expect JFreeChart to manage it on its own.

private JFreeChart getHistogramChart(String name, double[] dataArray) {
        String plotTitle = name;
        String xAxisLabel = "Length of transaction";
        String yAxis = "Frequency";
        PlotOrientation orientation = PlotOrientation.VERTICAL;


        HistogramDataset histogramDataset = new HistogramDataset();
        histogramDataset.setType(HistogramType.FREQUENCY);
        histogramDataset.addSeries(name, dataArray, dataArray.length,1,dataArray.length);

        boolean show = true;
        boolean toolTips = false;
        boolean urls = false;
        JFreeChart chart = ChartFactory.createHistogram(plotTitle, xAxisLabel, yAxis,
                histogramDataset, orientation, show, toolTips, urls);

        chart.setBackgroundPaint(Color.white);

        XYPlot plot = chart.getXYPlot();
        plot.setForegroundAlpha(0.75f);
        NumberAxis axis = (NumberAxis) plot.getDomainAxis();
        axis.setAutoRangeIncludesZero(false);
        NumberAxis rangeAxis = (NumberAxis) plot.getRangeAxis();
        rangeAxis.setNumberFormatOverride(NumberFormat.getIntegerInstance());
        return chart;
    }

I have data in two variants:

As a list - {2=696, 3=229, 4=123, 5=74, 6=42, 7=29, 8=8, 9=9, 10=9, 11=2, 12=3, 13=2, 15=1, 16=5, 17=1, 19=1, 22=1, 23=1, 24=2, 27=1, 28=1, 29=1, 39=2, 48=1, 56=2, 57=1, 63=1, 93=1, 95=1, 99=1, 146=1, 435=1}

And as a coresponding double matrix - [0.0, 696.0, 229.0, 123.0, 74.0, 42.0, 29.0, 8.0, 9.0, 9.0, 2.0, 3.0, 2.0, 0.0, 1.0, 5.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 2.0, 0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 2.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 2.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0]

In the result, the y-axis ends in 425 instead of 700 that I would expect because of value in the second bin.

Screenshot of histogram

Upvotes: 1

Views: 1389

Answers (1)

Marco13
Marco13

Reputation: 54659

The same question has recently been asked for python and matplotlib. It is not a duplicate, because the languages and libraries are totally different. But the reason for the ... let's say, "unexpected behavior" is the same: People don't seem to know what a histogram actually is...

So to restate this here: Visually, a histogram is a bar chart. Not more. Not less.

What makes it so special is the data that is shown in this bar chart. Namely, the frequencies of elements that fall in certain bins. (These bins are usually ranges of values, or single (discrete) values, as in your case). And while JFreeChart offers dedicated methods for creating histograms, these are intended for the case where you have "raw" data, and where the binning still has to be computed. In your case, the binning has already been done. The data that you have already is the frequencies (and thus, the bar heights).

So the data that you have can simply be shown as a bar chart.

But you should consider to find a different visual representation for that. Similar to the linked python example: The number of bins/bars somewhat exceeds the number of bars that can still be represented reasonably: Even 2500 pixels wide, and with a very small font, the labels are not readable any more. And given that there are 435 values, even without the labels, the bars could only be a few pixels wide on a standard desktop monitor.

Most of the values in the given array are 0 anyhow - 403 values, to be precise. That's what was shown in your chart: The bar at index 0 had a height of 403, because that's the frequency of the value 0 in your data. You might consider omitting these values, if your use case allows this.

However, here's an example of what the result (as a proper bar chart) could look like:

Histogram

Created with this example:

import java.awt.Color;
import java.awt.Font;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.CategoryAxis;
import org.jfree.chart.axis.CategoryLabelPositions;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.category.DefaultCategoryDataset;

public class FreeChartHistogram
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }

    private static void createAndShowGui()
    {
        JFrame frame = new JFrame();

        double dataArray[] =
        { 0.0, 696.0, 229.0, 123.0, 74.0, 42.0, 29.0, 8.0, 9.0, 9.0, 2.0, 3.0,
            2.0, 0.0, 1.0, 5.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 2.0, 0.0,
            0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            2.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 2.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0 };
        JFreeChart chart = getHistogramChart("Test", dataArray);
        ChartPanel chartPanel = new ChartPanel(chart);
        chartPanel.setMaximumDrawHeight(3000);
        chartPanel.setMaximumDrawWidth(3000);
        frame.add(chartPanel);

        frame.setSize(2500, 600);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private static JFreeChart getHistogramChart(String name, double[] dataArray)
    {
        String plotTitle = name;
        String xAxisLabel = "Length of transaction";
        String yAxis = "Frequency";
        PlotOrientation orientation = PlotOrientation.VERTICAL;

        DefaultCategoryDataset dataSet = new DefaultCategoryDataset();
        for (int i = 0; i < dataArray.length; i++)
        {
            dataSet.addValue(dataArray[i], (Integer) 0, (Integer) i);
        }
        boolean show = true;
        boolean toolTips = false;
        boolean urls = false;
        JFreeChart chart = ChartFactory.createBarChart(plotTitle, xAxisLabel,
            yAxis, dataSet, orientation, show, toolTips, urls);
        chart.setBackgroundPaint(Color.WHITE);

        // Set a very small font for the labels, and rotate them...
        CategoryPlot plot = chart.getCategoryPlot();
        CategoryAxis domainAxis = plot.getDomainAxis();
        domainAxis.setTickLabelFont(new Font("Dialog", Font.PLAIN, 8));
        domainAxis.setCategoryLabelPositions(CategoryLabelPositions.UP_90);

        return chart;
    }
}

(A side note: It is much more likely to get helpful answers when you include an MCVE in the question. Imagine trying to answer 5 Swing questions per day. You'd soon get sick of always having to embed the component code from the question into a JFrame and fix random compilation issues that are only caused by the asker not being willing to make answering a bit easier...)

Upvotes: 2

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