ChartDirector Ver 3.0 (C++ Edition)

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 could 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, using additional arguments when calling LineLayer.setSymbolScale. This feature 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.

Source Code Listing

[The following project is available in "cppdemo/bubble".]
#include "chartdir.h" int main(int argc, char *argv[]) { //The XYZ points for the bubble chart double dataX0[] = {150, 300, 1000, 1700}; double dataY0[] = {12, 60, 25, 65}; double dataZ0[] = {20, 50, 50, 85}; double dataX1[] = {500, 1000, 1300}; double dataY1[] = {35, 50, 75}; double dataZ1[] = {30, 55, 95}; //Create a XYChart object of size 450 x 420 pixels XYChart *c = new 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 12 pts Times Bold Italic font. Set the background and border color to //Transparent. c->addLegend(50, 30, false, "timesbi.ttf", 12)->setBackground(Transparent); //Add a title to the chart using 18 pts Times Bold Itatic font. c->addTitle("Product Comparison Chart", "timesbi.ttf", 18); //Add a title to the y axis using 12 pts Arial Bold Italic font c->yAxis()->setTitle("Capacity (tons)", "arialbi.ttf", 12); //Add a title to the x axis using 12 pts Arial Bold Italic font c->xAxis()->setTitle("Range (miles)", "arialbi.ttf", 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(DoubleArray(dataX0, sizeof(dataX0)/sizeof(*dataX0)), DoubleArray(dataY0, sizeof(dataY0)/sizeof(*dataY0)), "Technology AAA", CircleSymbol, 9, 0x80ff3333, 0x80ff3333)->setSymbolScale(DoubleArray( dataZ0, sizeof(dataZ0)/sizeof(*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(DoubleArray(dataX1, sizeof(dataX1)/sizeof(*dataX1)), DoubleArray(dataY1, sizeof(dataY1)/sizeof(*dataY1)), "Technology BBB", CircleSymbol, 9, 0x803333ff, 0x803333ff)->setSymbolScale(DoubleArray( dataZ1, sizeof(dataZ1)/sizeof(*dataZ1))); //output the chart c->makeChart("bubble.png"); //free up resources delete c; return 0; }