ChartDirector 6.0 (C++ Edition)

Scatter Trend Chart




This example demonstrates linear regression trend line fitting together with scatter layers.

The chart in this example has 4 layers - 2 scatter layers created using XYChart.addScatterLayer to show the data points, and two trend layers created using XYChart.addTrendLayer2 for the two trend lines.

Source Code Listing

[The following code is available in "cppdemo/scattertrend". 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[] = {50, 55, 37, 24, 42, 49, 63, 72, 83, 59};
    double dataY0[] = {3.6, 2.8, 2.5, 2.3, 3.8, 3.0, 3.8, 5.0, 6.0, 3.3};

    // The XY data of the second data series
    double dataX1[] = {50, 55, 37, 24, 42, 49, 63, 72, 83, 59};
    double dataY1[] = {1.6, 1.8, 0.8, 0.5, 1.3, 1.5, 2.3, 2.4, 2.9, 1.5};

    // 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 white background and a light
    // grey border (0xc0c0c0). Turn on both horizontal and vertical grid lines with light grey color
    // (0xc0c0c0)
    c->setPlotArea(55, 65, 350, 300, 0xffffff, -1, 0xc0c0c0, 0xc0c0c0, -1);

    // Add a legend box at (50, 30) (top of the chart) with horizontal layout. Use 12pt Times Bold
    // Italic font. Set the background and border color to Transparent.
    c->addLegend(50, 30, false, "timesbi.ttf", 12)->setBackground(Chart::Transparent);

    // Add a title to the chart using 18 point Times Bold Itatic font.
    c->addTitle("Server Performance", "timesbi.ttf", 18);

    // Add titles to the axes using 12pt Arial Bold Italic font
    c->yAxis()->setTitle("Response Time (sec)", "arialbi.ttf", 12);
    c->xAxis()->setTitle("Server Load (TPS)", "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]))), "Server AAA", Chart::DiamondSymbol, 11,
        0x008000);

    // Add a trend line layer for (dataX0, dataY0)
    c->addTrendLayer(DoubleArray(dataX0, (int)(sizeof(dataX0) / sizeof(dataX0[0]))), DoubleArray(
        dataY0, (int)(sizeof(dataY0) / sizeof(dataY0[0]))), 0x008000)->setLineWidth(3);

    // 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]))), "Server BBB", Chart::TriangleSymbol, 9,
        0x6666ff);

    // Add a trend line layer for (dataX1, dataY1)
    c->addTrendLayer(DoubleArray(dataX1, (int)(sizeof(dataX1) / sizeof(dataX1[0]))), DoubleArray(
        dataY1, (int)(sizeof(dataY1) / sizeof(dataY1[0]))), 0x6666ff)->setLineWidth(3);

    // Output the chart
    c->makeChart("scattertrend.png");

    //free up resources
    delete c;
    return 0;
}