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63 lines
2.8 KiB
Markdown
63 lines
2.8 KiB
Markdown
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# Example (JKQTPlotter): Barchart With Error Bars {#JKQTPlotterBarchartsErrorBars}
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This project (see [`barchart_errorbars`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/barchart_errorbars) shows how to draw barcharts with different styles of error indicators.
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The source code of the main application is (see [`barchart_errorbars.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/barchart_errorbars/barchart_errorbars.cpp):
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```.cpp
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// 1. create a plotter window and get a pointer to the internal datastore (for convenience)
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JKQTPDatastore* ds=plot.getDatastore();
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// 2. now we create three columns for key and value
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size_t columnK=ds->addLinearColumn(6, 0.4*JKQTPSTATISTICS_PI, 2.2*JKQTPSTATISTICS_PI,"k");
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size_t columnV=ds->addColumnCalculatedFromColumn(columnK, &cos, "v");
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size_t columnE=ds->addColumnCalculatedFromColumn(columnK, [](double x) { return 0.05+0.06*(1.0+sin(x)); }, "error");
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// 3. create a graph in the plot, which plots the dataset with symmetric:
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JKQTPBarVerticalErrorGraph* graph1=new JKQTPBarVerticalErrorGraph(&plot);
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graph1->setKeyColumn(columnK);
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graph1->setValueColumn(columnV);
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graph1->setBarErrorColumn(columnE);
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// set error indicator style
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graph1->setBarErrorStyle(JKQTPErrorBars);
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graph1->setTitle(QObject::tr("JKQTPErrorBars"));
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plot.addGraph(graph1);
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// 4. create a second graph in the plot, which plots the second dataset with outer error bars only:
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JKQTPBarVerticalErrorGraph* graph2=new JKQTPBarVerticalErrorGraph(&plot);
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graph2->setKeyColumn(columnK);
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graph2->setValueColumn(columnV);
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graph2->setBarErrorColumn(columnE);
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// set error indicator style
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graph2->setBarErrorStyle(JKQTPErrorHalfBarsOutwards);
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graph2->setTitle(QObject::tr("JKQTPErrorHalfBarsOutwards"));
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plot.addGraph(graph2);
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// 5. now we set the graphs, so they are plotted side-by-side
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// This function searches all JKQTPBarHorizontalGraph in the current
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// plot and sets their shift/scale so they form a nice plot with
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// side-by-side groups
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graph1->autoscaleBarWidthAndShift(0.9, 0.9);
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// 6 autoscale the plot so the graph is contained
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plot.zoomToFit();
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// 7. show plotter and make it a decent size
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plot.getPlotter()->setKeyPosition(JKQTPKeyInsideTopLeft);
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plot.setWindowTitle(title);
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plot.show();
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plot.resize(400,400);
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```
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The result looks like this:
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In order to draw horizontal error bars, you have to use `JKQTPBarHorizontalErrorGraph` instead of `JKQTPBarVerticalErrorGraph`:
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