ChartDirector 7.1 (C++ Edition)

Parametric Curve Fitting




This example demonstrates parametric curve fitting.

In addition to linear regression, ChartDirector also supports polynomial, exponential and logarithmic regression. To create these curves, a TrendLayer object is created using XYChart.addTrendLayer, and the regressive type is set using TrendLayer.setRegressionType.

Source Code Listing

The following is the command line version of the code in "cppdemo/paramcurve". The MFC version of the code is in "mfcdemo/mfcdemo". The Qt Widgets version of the code is in "qtdemo/qtdemo". The QML/Qt Quick version of the code is in "qmldemo/qmldemo".
#include "chartdir.h" int main(int argc, char *argv[]) { // The XY data of the first data series double dataX0[] = {10, 35, 17, 4, 22, 29, 45, 52, 63, 39}; const int dataX0_size = (int)(sizeof(dataX0)/sizeof(*dataX0)); double dataY0[] = {2.0, 3.2, 2.7, 1.2, 2.8, 2.9, 3.1, 3.0, 2.3, 3.3}; const int dataY0_size = (int)(sizeof(dataY0)/sizeof(*dataY0)); // The XY data of the second data series double dataX1[] = {30, 35, 17, 4, 22, 59, 43, 52, 63, 39}; const int dataX1_size = (int)(sizeof(dataX1)/sizeof(*dataX1)); double dataY1[] = {1.0, 1.3, 0.7, 0.6, 0.8, 3.0, 1.8, 2.3, 3.4, 1.5}; const int dataY1_size = (int)(sizeof(dataY1)/sizeof(*dataY1)); // The XY data of the third data series double dataX2[] = {28, 35, 15, 10, 22, 60, 46, 64, 39}; const int dataX2_size = (int)(sizeof(dataX2)/sizeof(*dataX2)); double dataY2[] = {2.0, 2.2, 1.2, 0.4, 1.8, 2.7, 2.4, 2.8, 2.4}; const int dataY2_size = (int)(sizeof(dataY2)/sizeof(*dataY2)); // Create a XYChart object of size 540 x 480 pixels XYChart* c = new XYChart(540, 480); // Set the plotarea at (70, 65) and of size 400 x 350 pixels, with white background and a light // grey border (0xc0c0c0). Turn on both horizontal and vertical grid lines with light grey color // (0xc0c0c0) c->setPlotArea(70, 65, 400, 350, 0xffffff, -1, 0xc0c0c0, 0xc0c0c0, -1); // Add a legend box with the top center point anchored at (270, 30). Use horizontal layout. Use // 10pt Arial Bold Italic font. Set the background and border color to Transparent. LegendBox* legendBox = c->addLegend(270, 30, false, "Arial Bold Italic", 10); legendBox->setAlignment(Chart::TopCenter); legendBox->setBackground(Chart::Transparent, Chart::Transparent); // Add a title to the chart using 18 point Times Bold Itatic font. c->addTitle("Parametric Curve Fitting", "Times New Roman Bold Italic", 18); // Add titles to the axes using 12pt Arial Bold Italic font c->yAxis()->setTitle("Axis Title Placeholder", "Arial Bold Italic", 12); c->xAxis()->setTitle("Axis Title Placeholder", "Arial Bold Italic", 12); // Set the axes line width to 3 pixels c->yAxis()->setWidth(3); c->xAxis()->setWidth(3); // Add a scatter layer using (dataX0, dataY0) c->addScatterLayer(DoubleArray(dataX0, dataX0_size), DoubleArray(dataY0, dataY0_size), "Polynomial", Chart::GlassSphere2Shape, 11, 0xff0000); // Add a degree 2 polynomial trend line layer for (dataX0, dataY0) TrendLayer* trend0 = c->addTrendLayer(DoubleArray(dataX0, dataX0_size), DoubleArray(dataY0, dataY0_size), 0xff0000); trend0->setLineWidth(3); trend0->setRegressionType(Chart::PolynomialRegression(2)); // Add a scatter layer for (dataX1, dataY1) c->addScatterLayer(DoubleArray(dataX1, dataX1_size), DoubleArray(dataY1, dataY1_size), "Exponential", Chart::GlassSphere2Shape, 11, 0x00aa00); // Add an exponential trend line layer for (dataX1, dataY1) TrendLayer* trend1 = c->addTrendLayer(DoubleArray(dataX1, dataX1_size), DoubleArray(dataY1, dataY1_size), 0x00aa00); trend1->setLineWidth(3); trend1->setRegressionType(Chart::ExponentialRegression); // Add a scatter layer using (dataX2, dataY2) c->addScatterLayer(DoubleArray(dataX2, dataX2_size), DoubleArray(dataY2, dataY2_size), "Logarithmic", Chart::GlassSphere2Shape, 11, 0x0000ff); // Add a logarithmic trend line layer for (dataX2, dataY2) TrendLayer* trend2 = c->addTrendLayer(DoubleArray(dataX2, dataX2_size), DoubleArray(dataY2, dataY2_size), 0x0000ff); trend2->setLineWidth(3); trend2->setRegressionType(Chart::LogarithmicRegression); // Output the chart c->makeChart("paramcurve.png"); //free up resources delete c; return 0; }