JKQtPlotter/examples/barchart_errorbars/README.md

Example (JKQTPlotter): Barchart With Error Bars

This project (see barchart_errorbars shows how to draw barcharts with different styles of error indicators.

The source code of the main application is (see barchart_errorbars.cpp:

    // 1. create a plotter window and get a pointer to the internal datastore (for convenience)
    JKQTPDatastore* ds=plot.getDatastore();

    // 2. now we create three columns for key and value
    size_t columnK=ds->addLinearColumn(6, 0.4*JKQTPSTATISTICS_PI, 2.2*JKQTPSTATISTICS_PI,"k");
    size_t columnV=ds->addColumnCalculatedFromColumn(columnK, &cos, "v");
    size_t columnE=ds->addColumnCalculatedFromColumn(columnK, [](double x) { return 0.05+0.06*(1.0+sin(x)); }, "error");

    // 3. create a graph in the plot, which plots the dataset with symmetric:
    JKQTPBarVerticalErrorGraph* graph1=new JKQTPBarVerticalErrorGraph(&plot);
    graph1->setKeyColumn(columnK);
    graph1->setValueColumn(columnV);
    graph1->setBarErrorColumn(columnE);
    // set error indicator style
    graph1->setBarErrorStyle(JKQTPErrorBars);
    graph1->setTitle(QObject::tr("JKQTPErrorBars"));
    plot.addGraph(graph1);

    // 4. create a second graph in the plot, which plots the second dataset with outer error bars only:
    JKQTPBarVerticalErrorGraph* graph2=new JKQTPBarVerticalErrorGraph(&plot);
    graph2->setKeyColumn(columnK);
    graph2->setValueColumn(columnV);
    graph2->setBarErrorColumn(columnE);
    // set error indicator style
    graph2->setBarErrorStyle(JKQTPErrorHalfBarsOutwards);
    graph2->setTitle(QObject::tr("JKQTPErrorHalfBarsOutwards"));
    plot.addGraph(graph2);

    // 5. now we set the graphs, so they are plotted side-by-side
    //    This function searches all JKQTPBarHorizontalGraph in the current
    //    plot and sets their shift/scale so they form a nice plot with
    //    side-by-side groups
    graph1->autoscaleBarWidthAndShift(0.9, 0.9);


    // 6 autoscale the plot so the graph is contained
    plot.zoomToFit();

    // 7. show plotter and make it a decent size
    plot.getPlotter()->setKeyPosition(JKQTPKeyInsideTopLeft);
    plot.setWindowTitle(title);
    plot.show();
    plot.resize(400,400);

The result looks like this:

In order to draw horizontal error bars, you have to use JKQTPBarHorizontalErrorGraph instead of JKQTPBarVerticalErrorGraph: