Area Line Chart

This example demonstrates an area chart with a line layer overlap on top. It also demonstrates using date/time x coordinates for the data points (as opposed to using x-axis labels), and also various methods to control the chart appearance.

In ChartDirector, x coordinates for the data points are optional. If no x coordinates are provided for the data points, the x coordinates will be assumed to be the array indexes (0, 1, 2, 3 ...), and the data points would be evenly spaced in the x direction. Axis labels specified using Axis.setLabels or Axis.setLabels2 are also positioned using the array indexes as the x coordinates, so the labels will match with the data points.

In some applications, it may be necessary or more convenient to provide x coordinates for the data points. For example, if the data points are unevenly spaced, or if there are multiple data series with different data point spacing in the x direction, x coordinates are needed. In this case, Layer.setXData or Layer.setXData2 can be used to provide the x coordinates. By default, ChartDirector will then automatically determine the x-axis scale and labels, just like how the y-axis is handled. The axis scale and labels can also be specified by using various Axis methods, such as Axis.setLinearScale, Axis.setLogScale and Axis.setDateScale (please refer to Axis for the full list).

Axis.setLabels or Axis.setLabels2 should not be used if x coordinates are provided, as they use array indexes as the x coordinates, which is unlikely to be consistent with the provided x coordinates.

In this example, x coordinates are used to demonstrate the automatic x-axis scale and labels.

The following is the command line version of the code in "cppdemo/arealine". 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[])
{
    // In this example, we simply use random data for the 2 data series.
    RanSeries* r = new RanSeries(127);
    DoubleArray data0 = r->getSeries(180, 70, -5, 5);
    DoubleArray data1 = r->getSeries(180, 150, -15, 15);
    DoubleArray timeStamps = r->getDateSeries(180, Chart::chartTime(2014, 3, 1), 86400);

    // Create a XYChart object of size 640 x 420 pixels
    XYChart* c = new XYChart(640, 420);

    // Add a title box using grey (0x555555) 20pt Arial Bold font
    c->addTitle("   Plasma Stabilizer Energy Usage", "Arial Bold", 20, 0x555555);

    // Set the plotarea at (70, 70) and of size 540 x 320 pixels, with transparent background and
    // border and light grey (0xcccccc) horizontal grid lines
    c->setPlotArea(70, 70, 540, 320, -1, -1, Chart::Transparent, 0xcccccc);

    // Add a legend box with horizontal layout above the plot area at (70, 32). Use 12pt Arial Bold
    // dark grey (0x555555) font, transparent background and border, and line style legend icon.
    LegendBox* b = c->addLegend(70, 32, false, "Arial Bold", 12);
    b->setFontColor(0x555555);
    b->setBackground(Chart::Transparent, Chart::Transparent);
    b->setLineStyleKey();

    // Set axis label font to 12pt Arial
    c->xAxis()->setLabelStyle("Arial", 12);
    c->yAxis()->setLabelStyle("Arial", 12);

    // Set the x and y axis stems to transparent, and the x-axis tick color to grey (0xaaaaaa)
    c->xAxis()->setColors(Chart::Transparent, Chart::TextColor, Chart::TextColor, 0xaaaaaa);
    c->yAxis()->setColors(Chart::Transparent);

    // Set the major/minor tick lengths for the x-axis to 10 and 0.
    c->xAxis()->setTickLength(10, 0);

    // For the automatic axis labels, set the minimum spacing to 80/40 pixels for the x/y axis.
    c->xAxis()->setTickDensity(80);
    c->yAxis()->setTickDensity(40);

    // Use "mm/yyyy" as the x-axis label format for the first plotted month of a year, and "mm" for
    // other months
    c->xAxis()->setMultiFormat(Chart::StartOfYearFilter(), "{value|mm/yyyy} ",
        Chart::StartOfMonthFilter(), "{value|mm}");

    // Add a title to the y axis using dark grey (0x555555) 12pt Arial Bold font
    c->yAxis()->setTitle("Energy (kWh)", "Arial Bold", 14, 0x555555);

    // Add a line layer with 2-pixel line width
    LineLayer* layer0 = c->addLineLayer(data0, 0xcc0000, "Power Usage");
    layer0->setXData(timeStamps);
    layer0->setLineWidth(2);

    // Add an area layer using semi-transparent blue (0x7f0044cc) as the fill color
    AreaLayer* layer1 = c->addAreaLayer(data1, 0x7f0044cc, "Effective Load");
    layer1->setXData(timeStamps);
    layer1->setBorderColor(Chart::SameAsMainColor);

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

    //free up resources
    delete r;
    delete c;

    return 0;
}