Discrete Heat Map

This example demonstrates the basic steps in creating a discrete heat map.

A discrete heat map consists of rectangular cells in a grid of which the cell color depends on its data value.

Create an XYChart object using XYChart.XYChart.
Specify the plot area of the chart using XYChart.setPlotArea. The plot area is the rectangle bounded by the x and y axes. You should leave some margin on the outside of the plot area for axis labels, chart titles, etc.
Add a discrete heat map layer using XYChart.addDiscreteHeatMapLayer.
Specify the labels on the x-axis and y-axis using Axis.setLabels. Shift the labels by 0.5 units using Axis.setOffset to align the labels with the cell center. (The default is to align the labels with the grid lines.)
The color axis (visually represented as the color legend) is positioned vertically to the right of the plot area using DiscreteHeatMapLayer.setColorAxis.
Pass the chart to the CChartViewer for display using CChartViewer.setChart (MFC version) or QChartViewer.setChart (Qt version), or generate the chart as an image file using BaseChart.makeChart (Command Line version).
Generate tool tips for the chart using BaseChart.getHTMLImageMap. (MFC/Qt version)

The following is the command line version of the code in "cppdemo/discreteheatmap". 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 x-axis and y-axis labels
    const char* xLabels[] = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J"};
    const int xLabels_size = (int)(sizeof(xLabels)/sizeof(*xLabels));
    const char* yLabels[] = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
    const int yLabels_size = (int)(sizeof(yLabels)/sizeof(*yLabels));

    // Random data for the 10 x 10 cells
    RanSeries* r = new RanSeries(2);
    DoubleArray zData = r->get2DSeries(xLabels_size, yLabels_size, 0, 100);

    // Create an XYChart object of size 520 x 470 pixels.
    XYChart* c = new XYChart(520, 470);

    // Set the plotarea at (50, 30) and of size 400 x 400 pixels.
    PlotArea* p = c->setPlotArea(50, 30, 400, 400);

    // Create a discrete heat map with 10 x 10 cells
    DiscreteHeatMapLayer* layer = c->addDiscreteHeatMapLayer(zData, xLabels_size);

    // Set the x-axis labels. Use 8pt Arial Bold font. Set axis stem to transparent, so only the
    // labels are visible. Set 0.5 offset to position the labels in between the grid lines.
    c->xAxis()->setLabels(StringArray(xLabels, xLabels_size));
    c->xAxis()->setLabelStyle("Arial Bold", 8);
    c->xAxis()->setColors(Chart::Transparent, Chart::TextColor);
    c->xAxis()->setLabelOffset(0.5);
    c->xAxis()->setTitle("X Axis Title Placeholder", "Arial Bold", 12);

    // Set the y-axis labels. Use 8pt Arial Bold font. Set axis stem to transparent, so only the
    // labels are visible. Set 0.5 offset to position the labels in between the grid lines.
    c->yAxis()->setLabels(StringArray(yLabels, yLabels_size));
    c->yAxis()->setLabelStyle("Arial Bold", 8);
    c->yAxis()->setColors(Chart::Transparent, Chart::TextColor);
    c->yAxis()->setLabelOffset(0.5);
    c->yAxis()->setTitle("Y Axis Title Placeholder", "Arial Bold", 12);

    // Position the color axis 20 pixels to the right of the plot area and of the same height as the
    // plot area. Put the labels on the right side of the color axis. Use 8pt Arial Bold font for
    // the labels.
    ColorAxis* cAxis = layer->setColorAxis(p->getRightX() + 20, p->getTopY(), Chart::TopLeft,
        p->getHeight(), Chart::Right);
    cAxis->setLabelStyle("Arial Bold", 8);

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

    //free up resources
    delete r;
    delete c;

    return 0;
}