Bubble charts are similar to scatter plots except they represent data with three dimensions. The first two dimensions are expressed on the X and Y axes and the third is represented by the size of the point plotted. This can be helpful in determining relationships between data values.

We will again use the DataTable class to initially hold the data to be displayed. In this example, we will read data from a sample file called MarriageByYears.csv. This is also a CSV file, and contains one column representing the year a marriage occurred, a second column holding the age at which a person was married, and a third column holding integers representing marital satisfaction on a scale from 1 (least satisfied) to 10 (most satisfied). We create a DataSeries to represent our type of desired data plot and then create a XYPlot object:

DataReader readType =  
    DataReaderFactory.getInstance().get("text/csv"); 
String fileName = "C://MarriageByYears.csv"; 
try { 
    DataTable bubbleData = (DataTable) readType.read( 
        new FileInputStream(fileName), Integer.class,  
            Integer.class, Integer.class); 
DataSeries bubbleSeries = new DataSeries("Bubble", bubbleData); 
XYPlot testPlot = new XYPlot(bubbleSeries); 
 

Next, we set basic property information about our chart. We will set the color and turn off the vertical and horizontal grids in this example. We will also make our X and Y axes invisible in this example. Notice that we still set a range for the axes, even though they are not displayed:

 
testPlot.setInsets(new Insets2D.Double(30.0));  testPlot.setBackground(new Color(0.75f, 0.75f, 0.75f)); 
XYPlotArea2D areaProp = (XYPlotArea2D) testPlot.getPlotArea(); 
areaProp.setBorderColor(null);    
areaProp.setMajorGridX(false);    
areaProp.setMajorGridY(false);    
areaProp.setClippingArea(null);   
 
testPlot.getAxisRenderer(XYPlot.AXIS_X).setShapeVisible(false);   
testPlot.getAxisRenderer(XYPlot.AXIS_X).setTicksVisible(false);   
testPlot.getAxisRenderer(XYPlot.AXIS_Y).setShapeVisible(false);   
testPlot.getAxisRenderer(XYPlot.AXIS_Y).setTicksVisible(false);   
testPlot.getAxis(XYPlot.AXIS_X).setRange(1940, 2020);   
testPlot.getAxis(XYPlot.AXIS_Y).setRange(17, 30);   
 

We can also set properties related to the bubbles drawn on the chart. Here, we set the color and shape, and specify which column of the data will be used to scale the shapes. In this case, the third column, with the marital satisfaction rating, will be used. We set it using the setColumn method:

Color color = GraphicsUtils.deriveWithAlpha(Color.black, 96); 
SizeablePointRenderer renderBubble = new SizeablePointRenderer(); 
renderBubble.setShape(new Ellipse2D.Double(-3.5, -3.5, 4.0, 4.0));   
renderBubble.setColor(color); 
renderBubble.setColumn(2);   
testPlot.setPointRenderers(bubbleSeries, renderBubble);   
 

Finally, we create our panel and set its size:

 
add(new InteractivePanel(testPlot), BorderLayout.CENTER);  
setSize(new Dimension(1500, 700)); 
setVisible(true); 
 

When the application is executed, the following graph is displayed. Notice both the size and color of the points changes depending upon the frequency of that particular data point: