Bubble Chart

This example demonstrates how to create a bubble chart.

In ChartDirector, a bubble chart can be created as a scatter layer with circles as symbols using XYChart.addScatterLayer. The sizes of the symbols are then controlled by another data series (z data) using LineLayer.setSymbolScale. This creates circles of different sizes.

By default, ChartDirector handles z data using pixel units. That means a z value of 50 will result in a symbol size of 50 pixels. If your z data are too small or too large, you may re-scale them using ArrayMath.mul before passing them to LineLayer.setSymbolScale.

ChartDirector also supports handling the z data using the same scale as the y (or x) axis by supplying additional arguments to LineLayer.setSymbolScale. This is useful if the symbol sizes reflect some features of the y (or x) data, such as the standard deviation or confidence of the y (or x) value.

pythondemo\bubble.py

#!/usr/bin/python

# The ChartDirector for Python module is assumed to be in "../lib"
import sys, os
sys.path.insert(0, os.path.join(os.path.abspath(sys.path[0]), "..", "lib"))

from pychartdir import *

# The XYZ points for the bubble chart
dataX0 = [150, 300, 1000, 1700]
dataY0 = [12, 60, 25, 65]
dataZ0 = [20, 50, 50, 85]

dataX1 = [500, 1000, 1300]
dataY1 = [35, 50, 75]
dataZ1 = [30, 55, 95]

# Create a XYChart object of size 450 x 420 pixels
c = XYChart(450, 420)

# Set the plotarea at (55, 65) and of size 350 x 300 pixels, with a light grey border (0xc0c0c0).
# Turn on both horizontal and vertical grid lines with light grey color (0xc0c0c0)
c.setPlotArea(55, 65, 350, 300, -1, -1, 0xc0c0c0, 0xc0c0c0, -1)

# Add a legend box at (50, 30) (top of the chart) with horizontal layout. Use 12pt Times Bold Italic
# font. Set the background and border color to Transparent.
c.addLegend(50, 30, 0, "Times New Roman Bold Italic", 12).setBackground(Transparent)

# Add a title to the chart using 18pt Times Bold Itatic font.
c.addTitle("Product Comparison Chart", "Times New Roman Bold Italic", 18)

# Add a title to the y axis using 12pt Arial Bold Italic font
c.yAxis().setTitle("Capacity (tons)", "Arial Bold Italic", 12)

# Add a title to the x axis using 12pt Arial Bold Italic font
c.xAxis().setTitle("Range (miles)", "Arial Bold Italic", 12)

# Set the axes line width to 3 pixels
c.xAxis().setWidth(3)
c.yAxis().setWidth(3)

# Add (dataX0, dataY0) as a scatter layer with semi-transparent red (0x80ff3333) circle symbols,
# where the circle size is modulated by dataZ0. This creates a bubble effect.
c.addScatterLayer(dataX0, dataY0, "Technology AAA", CircleSymbol, 9, 0x80ff3333, 0x80ff3333
    ).setSymbolScale(dataZ0)

# Add (dataX1, dataY1) as a scatter layer with semi-transparent green (0x803333ff) circle symbols,
# where the circle size is modulated by dataZ1. This creates a bubble effect.
c.addScatterLayer(dataX1, dataY1, "Technology BBB", CircleSymbol, 9, 0x803333ff, 0x803333ff
    ).setSymbolScale(dataZ1)

# Output the chart
c.makeChart("bubble.png")