ChartDirector Ver 3.0 (C++ Edition)

Y-Axis Scaling


        

This example illustrates how to control scaling of an axis.

By default, ChartDirector will auto-scaled all axes. The Axis.setAutoScale method controls the top extension, bottom extension and the zero affinity parameters that ChartDirector uses during auto-scaling. The first three charts demonstrates the effects of different top/bottom extensions. (Please refer to Axis.setAutoScale on what these parameters mean.)

The fourth chart demonstrates that one could exclude a segment on the ends of an axis from scaling using Axis.setMargin.

The fifth chart demonstrates using manual scaling instead of auto-scaling. A manual linear scale can be configured using Axis.setLinearScale or Axis.setLinearScale2. ChartDirector also supports Axis.setLogScale, Axis.setLogScale2, Axis.setDateScale and Axis.setDateScale2 for configuring manual log and date scales.

Source Code Listing

[The following project is available in "cppdemo/axisscale".]
#include "chartdir.h" void createChart(int img, const char *filename) { //The data for the chart double data[] = {5.5, 3.5, -3.7, 1.7, -1.4, 3.3}; const char *labels[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun"}; //Create a XYChart object of size 200 x 180 pixels XYChart *c = new XYChart(200, 180); //Set the plot area at (30, 20) and of size 140 x 130 pixels c->setPlotArea(30, 20, 140, 130); //Configure the axis as according to the input parameter if (img == 0) { c->addTitle("No Axis Extension", "arial.ttf", 8); } else if (img == 1) { c->addTitle("Top/Bottom Extensions = 0/0", "arial.ttf", 8); //Reserve 20% margin at top of plot area when auto-scaling c->yAxis()->setAutoScale(0, 0); } else if (img == 2) { c->addTitle("Top/Bottom Extensions = 0.2/0.2", "arial.ttf", 8); //Reserve 20% margin at top and bottom of plot area when auto-scaling c->yAxis()->setAutoScale(0.2, 0.2); } else if (img == 3) { c->addTitle("Axis Top Margin = 15", "arial.ttf", 8); //Reserve 15 pixels at top of plot area c->yAxis()->setMargin(15); } else { c->addTitle("Manual Scale -5 to 10", "arial.ttf", 8); //Set the y axis to scale from -5 to 10, with ticks every 5 units c->yAxis()->setLinearScale(-5, 10, 5); } //Set the labels on the x axis c->xAxis()->setLabels(StringArray(labels, sizeof(labels)/sizeof(*labels))); //Add a color bar layer using the given data. Use a 1 pixel 3D border for //the bars. c->addBarLayer(DoubleArray(data, sizeof(data)/sizeof(*data)), IntArray(0, 0) )->setBorderColor(-1, 1); //output the chart c->makeChart(filename); //free up resources delete c; } int main(int argc, char *argv[]) { createChart(0, "axisscale0.png"); createChart(1, "axisscale1.png"); createChart(2, "axisscale2.png"); createChart(3, "axisscale3.png"); createChart(4, "axisscale4.png"); return 0; }