Example (JKQTPlotter): Parametrized Scatter-graph with custom symbols

This project (see ./examples/paramscatterplot_customsymbol/) demonstrates using JKQTPlotter to draw a parametrized scatter graph (JKQTPXYParametrizedScatterGraph) with custom symbols. To demonstrate this, we create a plot with several symbols, connected by a line, where each symbol shows a pie-chart with varying fractions.

The source code of the example can be found in paramscatterplot_customsymbol.cpp.

First we create a plotter window and get a pointer to the internal datastore (for convenience). Then we add three new datacolumns and obtain back inserters.

JKQTPlotter plot;
JKQTPDatastore* ds=plot.getDatastore();
 
size_t columnX=ds->addColumn("x");
auto colXInserter=ds->backInserter(columnX);
size_t columnY=ds->addColumn("y");
auto colYInserter=ds->backInserter(columnY);
size_t columnS=ds->addColumn("sym");
auto colSInserter=ds->backInserter(columnS);

Now we define a functor that draws a pie chart with three segments with fractions f1 (blue), f2 (green) and 1.0-f1-f2 (yellow):

auto pieFunc=[](QPainter& p, double f1, double f2) {
        double f3=1.0-f1-f2;
        QRectF rec(-0.5,-0.5,1,1);
        p.setPen(QPen(QColor("black"), p.pen().width(), Qt::SolidLine));
        p.setBrush(QBrush(QColor("blue")));
        p.drawPie(rec, 90, -f1*360*16);
        p.setBrush(QBrush(QColor("green")));
        p.drawPie(rec, 90-f1*360*16, -f2*360*16);
        p.setBrush(QBrush(QColor("yellow")));
        p.drawPie(rec, 90-(f1+f2)*360*16, -f3*360*16);
    };

Now we create data for the plot, x and y follow a simple function and the symbols are encoded in a separated column, where for each datapoint, we register a new symbol using JKQTPRegisterCustomGraphSymbol(), which is drawn by a differently parametrized (f1,f2) functor pieFunc.

const int Ndata=5;
for (int i=0; i<Ndata; i++) {
    // put data
    const double x=double(i)/double(Ndata-1);
    *(colXInserter++)=x;
    *(colYInserter++)=pow(x*1.3, 2.0);
    *(colSInserter++)=JKQTPRegisterCustomGraphSymbol(std::bind(pieFunc, std::placeholders::_1, x*0.4, 0.5-x*0.2));
}

Finally we create a graph in the plot, which displays our datasets:

JKQTPXYParametrizedScatterGraph* graph1=new JKQTPXYParametrizedScatterGraph(&plot);
graph1->setXColumn(columnX);
graph1->setYColumn(columnY);
graph1->setSymbolSize(25);
graph1->setDrawLine(true);
graph1->setLineWidth(4);
graph1->setDrawLineInForeground(false);
graph1->setColor(QColor("black"));
graph1->setTitle(QObject::tr("pie scatter"));

The symbol type is stored in columnS, note however how we have to give a custom JKQTPXYParametrizedScatterGraph::symbolColumnFunctor, because the default one maps the values in the column to the range [0...JKQTPMaxSymbolID] in a cycling fashion (using a mod operation), but here we want to use the `stored ID directly.

graph1->setSymbolColumn(columnS);
graph1->setSymbolColumnFunctor(std::bind([](double /*x*/, double /*y*/, double symbolcolumn)->JKQTPGraphSymbols {
    return static_cast<JKQTPGraphSymbols>(floor(symbolcolumn));
}, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
plot.addGraph(graph1);

The result looks like this: