ChartDirector 7.0 (Python Edition)

Variable Width Bar Chart



This example demonstrates a bar chart with variable bar widths.

ChartDirector does not really have a bar layer for variable width bars. However, an area layer can be used to create the same effect.

The variable width bars in this example are actually 4 areas, created by 4 area layers. The data set for each area layer consists of 4 points for the 4 corners of a bar.

Source Code Listing

pythondemo\varwidthbar.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 data for the chart data = [800, 600, 1000, 1400] widths = [250, 500, 960, 460] labels = ["Wind", "Hydro", "Coal", "Natural Gas"] # The colors to use colors = [0x00aa00, 0x66aaee, 0xee6622, 0xffbb00] # Create a XYChart object of size 500 x 350 pixels c = XYChart(500, 350) # Add a title to the chart using 15pt Arial Italic font c.addTitle("Energy Generation Breakdown", "Arial Italic", 15) # Set the plotarea at (60, 60) and of (chart_width - 90) x (chart_height - 100) in size. Use a # vertical gradient color from light blue (f9f9ff) to sky blue (aaccff) as background. Set grid # lines to white (ffffff). plotAreaBgColor = c.linearGradientColor(0, 60, 0, c.getHeight() - 40, 0xaaccff, 0xf9fcff) c.setPlotArea(60, 60, c.getWidth() - 90, c.getHeight() - 100, plotAreaBgColor, -1, -1, 0xffffff) # Add a legend box at (50, 30) using horizontal layout and transparent background. c.addLegend(55, 30, 0).setBackground(Transparent) # Add titles to x/y axes with 10 points Arial Bold font c.xAxis().setTitle("Mega Watts", "Arial Bold", 10) c.yAxis().setTitle("Cost per MWh (dollars)", "Arial Bold", 10) # Set the x axis rounding to false, so that the x-axis will fit the data exactly c.xAxis().setRounding(0, 0) # In ChartDirector, there is no bar layer that can have variable bar widths, but you may create a # bar using an area layer. (A bar can be considered as the area under a rectangular outline.) So by # using a loop to create one bar per area layer, we can achieve a variable width bar chart. # starting position of current bar currentX = 0 for i in range(0, len(data)) : # ending position of current bar nextX = currentX + widths[i] # outline of the bar dataX = [currentX, currentX, nextX, nextX] dataY = [0, data[i], data[i], 0] # create the area layer to fill the bar layer = c.addAreaLayer(dataY, colors[i], labels[i]) layer.setXData(dataX) # the ending position becomes the starting position of the next bar currentX = nextX # Output the chart c.makeChart("varwidthbar.png")

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