ChartDirector Ver 5.0 (C++ Edition)

Uneven Data Points




This example demonstrates data series that are unevenly spaced in the x dimension.

In ChartDirector, it is only necessarily to provide the y coordinates (the data values) to plot a line. The x coordinates are optional. If no x coordinates are provided, the data points are assumed to be evenly spaced on the x dimension. In such case, the x-axis can be used to label the data points, with the labels configured using Axis.setLabels or Axis.setLabels2. The labels are only for human reading and will not affect the positioning of the data points.

On the other hand, if the data points are unevenly spaced, or if there are multiple data series with different spacing in the x dimension, it is necessary to provide the x coordinates of the data series. They can be provided using Layer.setXData or Layer.setXData2. In such case, the x-axis can be automatically scaled, with labels generated by ChartDirector. Alternatively, Axis.setLinearScale, Axis.setLogScale, Axis.setDateScale, etc., can be used to explicitly set a scale of the x-axis. Axis.setLabels or Axis.setLabels2 should not be used for charts that use real x coordinates.

In this example, the red line has unevenly spaced x coordinates, set using Layer.setXData. Both the green line and the orange line has evenly spaced x coordinates, but the spacing in the x dimension differs between the lines. Their x coordinates are set using Layer.setXData2. Note that the lines start and end at different x coordinates, and they do not need to span the entire x-axis range. The x-axis in this example is automatically scaled.

Source Code Listing

[The following code is available in "cppdemo/unevenpoints". 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[])
{
    // Data points which more unevenly spaced in time
    double data0Y[] = {62, 69, 53, 58, 84, 76, 49, 61, 64, 77, 79};
    double data0X[] = {chartTime(2007, 1, 1), chartTime(2007, 1, 2), chartTime(2007,
        1, 5), chartTime(2007, 1, 7), chartTime(2007, 1, 10), chartTime(2007, 1, 14),
        chartTime(2007, 1, 17), chartTime(2007, 1, 18), chartTime(2007, 1, 19),
        chartTime(2007, 1, 20), chartTime(2007, 1, 21)};

    // Data points which are evenly spaced in a certain time range
    double data1Y[] = {36, 25, 28, 38, 20, 30, 27, 35, 65, 60, 40, 73, 62, 90, 75, 72
        };
    double data1Start = chartTime(2007, 1, 1);
    double data1End = chartTime(2007, 1, 16);

    // Data points which are evenly spaced in another time range, in which the
    // spacing is different from the above series
    double data2Y[] = {25, 15, 30, 23, 32, 55, 45};
    double data2Start = chartTime(2007, 1, 9);
    double data2End = chartTime(2007, 1, 21);

    // Create a XYChart object of size 600 x 400 pixels. Use a vertical gradient
    // color from light blue (99ccff) to white (ffffff) spanning the top 100 pixels
    // as background. Set border to grey (888888). Use rounded corners. Enable soft
    // drop shadow.
    XYChart *c = new XYChart(600, 400);
    c->setBackground(c->linearGradientColor(0, 0, 0, 100, 0x99ccff, 0xffffff),
        0x888888);
    c->setRoundedFrame();
    c->setDropShadow();

    // Add a title using 18 pts Times New Roman Bold Italic font. #Set top margin to
    // 16 pixels.
    c->addTitle("Product Line Order Backlog", "timesbi.ttf", 18)->setMargin(0, 0, 16,
        0);

    // Set the plotarea at (60, 80) and of 510 x 275 pixels in size. Use transparent
    // border and dark grey (444444) dotted grid lines
    PlotArea *plotArea = c->setPlotArea(60, 80, 510, 275, -1, -1, Chart::Transparent,
        c->dashLineColor(0x444444, 0x000101), -1);

    // Add a legend box where the top-center is anchored to the horizontal center of
    // the plot area at y = 45. Use horizontal layout and 10 points Arial Bold font,
    // and transparent background and border.
    LegendBox *legendBox = c->addLegend(plotArea->getLeftX() + plotArea->getWidth() /
        2, 45, false, "arialbd.ttf", 10);
    legendBox->setAlignment(Chart::TopCenter);
    legendBox->setBackground(Chart::Transparent, Chart::Transparent);

    // Set x-axis tick density to 75 pixels and y-axis tick density to 30 pixels.
    // ChartDirector auto-scaling will use this as the guidelines when putting ticks
    // on the x-axis and y-axis.
    c->yAxis()->setTickDensity(30);
    c->xAxis()->setTickDensity(75);

    // Set all axes to transparent
    c->xAxis()->setColors(Chart::Transparent);
    c->yAxis()->setColors(Chart::Transparent);

    // Set the x-axis margins to 15 pixels, so that the horizontal grid lines can
    // extend beyond the leftmost and rightmost vertical grid lines
    c->xAxis()->setMargin(15, 15);

    // Set axis label style to 8pts Arial Bold
    c->xAxis()->setLabelStyle("arialbd.ttf", 8);
    c->yAxis()->setLabelStyle("arialbd.ttf", 8);
    c->yAxis2()->setLabelStyle("arialbd.ttf", 8);

    // Add axis title using 10pts Arial Bold Italic font
    c->yAxis()->setTitle("Backlog in USD millions", "arialbi.ttf", 10);

    // Add the first data series
    LineLayer *layer0 = c->addLineLayer();
    layer0->addDataSet(DoubleArray(data0Y, sizeof(data0Y)/sizeof(data0Y[0])),
        0xff0000, "Quantum Computer")->setDataSymbol(Chart::GlassSphere2Shape, 11);
    layer0->setXData(DoubleArray(data0X, sizeof(data0X)/sizeof(data0X[0])));
    layer0->setLineWidth(3);

    // Add the second data series
    LineLayer *layer1 = c->addLineLayer();
    layer1->addDataSet(DoubleArray(data1Y, sizeof(data1Y)/sizeof(data1Y[0])),
        0x00ff00, "Atom Synthesizer")->setDataSymbol(Chart::GlassSphere2Shape, 11);
    layer1->setXData(data1Start, data1End);
    layer1->setLineWidth(3);

    // Add the third data series
    LineLayer *layer2 = c->addLineLayer();
    layer2->addDataSet(DoubleArray(data2Y, sizeof(data2Y)/sizeof(data2Y[0])),
        0xff6600, "Proton Cannon")->setDataSymbol(Chart::GlassSphere2Shape, 11);
    layer2->setXData(data2Start, data2End);
    layer2->setLineWidth(3);

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

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