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61 lines
2.6 KiB
Markdown
61 lines
2.6 KiB
Markdown
# Example (JKQTPlotter): Simple Graph Labels Example {#JKQTPlotterGraphLabelsExample}
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This project (see [`graphlabels`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/graphlabels) demonstrates the use of JKQTPXYGraphLabels to add labels to the datapoints of a graph.
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The source code of the main application is (see [`graphlabels.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/graphlabels/graphlabels.cpp).
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Here is a short summary of the important parts of the code:
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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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JKQTPlotter plot;
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JKQTPDatastore* ds=plot.getDatastore();
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// 2. make up some arbitrary data to be used for plotting
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const size_t columnX=ds->addLinearColumn(Ndata, -1,1,"x");
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const size_t columnY=ds->addCalculatedColumnFromColumn(columnX, [](double x) { return jkqtp_roundToDigits(-sin(x*3.0),2);}, "data");
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// 3. create barchart and line-chart to display the data:
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// 3.1 Barcart:
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JKQTPBarVerticalGraph* graph1=new JKQTPBarVerticalGraph(&plot);
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graph1->setBarPositionColumn(columnX);
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graph1->setBarHeightColumn(columnY);
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graph1->setTitle(QObject::tr("dataset: bars"));
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graph1->setColor(QColorWithAlphaF(graph1->getFillColor(),0.25));
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// 3.2: LineChart:
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JKQTPXYLineGraph* graph2=new JKQTPXYLineGraph(&plot);
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graph2->setXColumn(columnX);
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graph2->setYColumn(columnY);
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graph2->setTitle(QObject::tr("dataset: lines"));
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graph2->setColor(QColorWithAlphaF(graph2->getLineColor(),0.5));
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// 4. now we add the data labels:
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// 4.1. create a JKQTPXYGraphLabels instance that displays the y-values at each location:
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JKQTPXYGraphLabels* graphLabels=new JKQTPXYGraphLabels(JKQTPXYGraphLabels::YValueLabel, &plot);
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// use the same (x,y) dataset as above. This is used on the one hand to derive the position of the label and on the other hand the label contents
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graphLabels->setXColumn(graph1->getXColumn());
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graphLabels->setYColumn(graph1->getYColumn());
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// 4.2. set position of labels and some styling options
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graphLabels->setLabelPosition(JKQTPGLabelAwayFromXAxis);
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graphLabels->setTextFontSize(14);
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// 5. add the graphs to the plot, so it is actually displayed
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plot.addGraph(graph1);
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plot.addGraph(graph2);
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plot.addGraph(graphLabels);
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```
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The result looks like this:
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or this:
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