ChartDirector 7.0 (C++ Edition)

Heat Map Cell Labels




This example demonstrates adding labels to the cells, adding gaps between cells and using a custom color scale.

This example is similar to Discrete Heat Map, with the following additions:

Source Code Listing

[The following code is available in "cppdemo/heatmapcelllabels". 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 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* rand = new RanSeries(2);
    DoubleArray zData = rand->get2DSeries(xLabels_size, yLabels_size, 0, 100);

    // We set the middle 5 x 5 cells to NoValue to remove them from the chart
    for(int x = 3; x < 7; ++x) {
        for(int y = 3; y < 7; ++y) {
            ((double*)(zData.data))[y * xLabels_size + x] = Chart::NoValue;
        }
    }

    // Create an XYChart object of size 480 x 540 pixels.
    XYChart* c = new XYChart(480, 540);

    // Set the plotarea at (50, 40) and of size 400 x 400 pixels. Set the background, border, and
    // grid lines to transparent.
    PlotArea* p = c->setPlotArea(50, 40, 400, 400, -1, -1, Chart::Transparent, Chart::Transparent);

    // 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. Position
    // the x-axis at the top of the chart.
    c->xAxis()->setLabels(StringArray(xLabels, xLabels_size));
    c->xAxis()->setLabelStyle("arialbd.ttf", 8);
    c->xAxis()->setColors(Chart::Transparent, Chart::TextColor);
    c->xAxis()->setLabelOffset(0.5);
    c->xAxis()->setTitle("X axis title placeholder", "arialbd.ttf", 12);
    c->setXAxisOnTop();

    // 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. Reverse
    // the y-axis so that the labels are flowing top-down instead of bottom-up.
    c->yAxis()->setLabels(StringArray(yLabels, yLabels_size));
    c->yAxis()->setLabelStyle("arialbd.ttf", 8);
    c->yAxis()->setColors(Chart::Transparent, Chart::TextColor);
    c->yAxis()->setLabelOffset(0.5);
    c->yAxis()->setTitle("Y axis title placeholder", "arialbd.ttf", 12);
    c->yAxis()->setReverse();

    // Set a 3-pixel gap between cells
    layer->setCellGap(3);

    // Use the z value as the cell label
    layer->setDataLabelFormat("{z|0}");

    // Position the color axis 20 pixels below the plot area and of the width as the plot area. Put
    // the labels at the bottom side of the color axis. Use 8pt Arial Bold font for the labels.
    ColorAxis* cAxis = layer->setColorAxis(p->getLeftX(), p->getBottomY() + 20, Chart::TopLeft,
        p->getWidth(), Chart::Bottom);
    cAxis->setLabelStyle("arialbd.ttf", 8);
    cAxis->setTitle("Color legend title placeholder", "arialbd.ttf", 12);

    // Set the color stops and scale of the color axis
    double colorScale[] = {0, 0x00ff00, 50, 0xffff00, 80, 0xff6600, 100, 0xff0000};
    const int colorScale_size = (int)(sizeof(colorScale)/sizeof(*colorScale));
    cAxis->setColorScale(DoubleArray(colorScale, colorScale_size));
    cAxis->setLinearScale(0, 100, 10);

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

    //free up resources
    delete rand;
    delete c;

    return 0;
}