ChartDirector 6.0 (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 code is available in "cppdemo/paramcurve". A MFC version of the code is available in "mfcdemo/mfcdemo" (Windows edition only). A QT version of the code is available in "qtdemo/qtdemo".]
 ```#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}; double dataY0[] = {2.0, 3.2, 2.7, 1.2, 2.8, 2.9, 3.1, 3.0, 2.3, 3.3}; // The XY data of the second data series double dataX1[] = {30, 35, 17, 4, 22, 59, 43, 52, 63, 39}; double dataY1[] = {1.0, 1.3, 0.7, 0.6, 0.8, 3.0, 1.8, 2.3, 3.4, 1.5}; // The XY data of the third data series double dataX2[] = {28, 35, 15, 10, 22, 60, 46, 64, 39}; double dataY2[] = {2.0, 2.2, 1.2, 0.4, 1.8, 2.7, 2.4, 2.8, 2.4}; // 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, "arialbi.ttf", 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", "timesbi.ttf", 18); // Add titles to the axes using 12pt Arial Bold Italic font c->yAxis()->setTitle("Axis Title Placeholder", "arialbi.ttf", 12); c->xAxis()->setTitle("Axis Title Placeholder", "arialbi.ttf", 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, (int)(sizeof(dataX0) / sizeof(dataX0[0]))), DoubleArray( dataY0, (int)(sizeof(dataY0) / sizeof(dataY0[0]))), "Polynomial", Chart::GlassSphere2Shape, 11, 0xff0000); // Add a degree 2 polynomial trend line layer for (dataX0, dataY0) TrendLayer *trend0 = c->addTrendLayer(DoubleArray(dataX0, (int)(sizeof(dataX0) / sizeof(dataX0[0 ]))), DoubleArray(dataY0, (int)(sizeof(dataY0) / sizeof(dataY0[0]))), 0xff0000); trend0->setLineWidth(3); trend0->setRegressionType(Chart::PolynomialRegression(2)); // Add a scatter layer for (dataX1, dataY1) c->addScatterLayer(DoubleArray(dataX1, (int)(sizeof(dataX1) / sizeof(dataX1[0]))), DoubleArray( dataY1, (int)(sizeof(dataY1) / sizeof(dataY1[0]))), "Exponential", Chart::GlassSphere2Shape, 11, 0x00aa00); // Add an exponential trend line layer for (dataX1, dataY1) TrendLayer *trend1 = c->addTrendLayer(DoubleArray(dataX1, (int)(sizeof(dataX1) / sizeof(dataX1[0 ]))), DoubleArray(dataY1, (int)(sizeof(dataY1) / sizeof(dataY1[0]))), 0x00aa00); trend1->setLineWidth(3); trend1->setRegressionType(Chart::ExponentialRegression); // Add a scatter layer using (dataX2, dataY2) c->addScatterLayer(DoubleArray(dataX2, (int)(sizeof(dataX2) / sizeof(dataX2[0]))), DoubleArray( dataY2, (int)(sizeof(dataY2) / sizeof(dataY2[0]))), "Logarithmic", Chart::GlassSphere2Shape, 11, 0x0000ff); // Add a logarithmic trend line layer for (dataX2, dataY2) TrendLayer *trend2 = c->addTrendLayer(DoubleArray(dataX2, (int)(sizeof(dataX2) / sizeof(dataX2[0 ]))), DoubleArray(dataY2, (int)(sizeof(dataY2) / sizeof(dataY2[0]))), 0x0000ff); trend2->setLineWidth(3); trend2->setRegressionType(Chart::LogarithmicRegression); // Output the chart c->makeChart("paramcurve.png"); //free up resources delete c; return 0; }```