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106 lines
4.9 KiB
Markdown
106 lines
4.9 KiB
Markdown
# Example (JKQTPlotter): Simple barchart {#JKQTPlotterBarcharts}
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This project (see [`barchart`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/barchart) simply creates a JKQTPlotter widget (as a new window) and adds several barcharts. They are ordered in groups.
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The source code of the main application is (see [`barchart.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/barchart/barchart.cpp):
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```.cpp
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#include <QApplication>
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#include "jkqtplotter/jkqtplotter.h"
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#include "jkqtplotter/graphs/jkqtpbarchart.h"
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#define Ndata 5
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int main(int argc, char* argv[])
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{
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QApplication app(argc, argv);
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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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plot.getPlotter()->setUseAntiAliasingForGraphs(true); // nicer (but slower) plotting
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plot.getPlotter()->setUseAntiAliasingForSystem(true); // nicer (but slower) plotting
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plot.getPlotter()->setUseAntiAliasingForText(true); // nicer (but slower) text rendering
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JKQTPDatastore* ds=plot.getDatastore();
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// 2. now we create data for three simple barchart
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QString L[Ndata]={ "cat. A", "cat. B", "cat. C", "cat. D", "other"};
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double X[Ndata]={ 1, 2, 3, 4, 5};
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double Y1[Ndata]={ 5, 4, 3, 4, 5};
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double Y2[Ndata]={ -5, -3, 1, 3, 6};
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double Y3[Ndata]={ 6, 2, 5, 3, 6};
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// 3. make data available to JKQTPlotter by adding it to the internal datastore.
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// Note: In this step the data is copied (of not specified otherwise)
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// the variables columnX and columnY... will contain the internal column ID of the
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// newly created columns with names "x" and "y..." and the (copied) data from X
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// and Y...
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size_t columnX=ds->addCopiedColumn(X, Ndata, "x");
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size_t columnY1=ds->addCopiedColumn(Y1, Ndata, "y1");
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size_t columnY2=ds->addCopiedColumn(Y2, Ndata, "y2");
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size_t columnY3=ds->addCopiedColumn(Y3, Ndata, "y3");
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// 4. create graphs in the plot, which plots the dataset X/Y1, X/Y2 and X/Y3:
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JKQTPBarVerticalGraph* graph1=new JKQTPBarVerticalGraph(&plot);
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graph1->setXColumn(columnX);
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graph1->setYColumn(columnY1);
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graph1->setTitle(QObject::tr("dataset 1"));
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JKQTPBarVerticalGraph* graph2=new JKQTPBarVerticalGraph(&plot);
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graph2->setXColumn(columnX);
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graph2->setYColumn(columnY2);
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graph2->setTitle(QObject::tr("dataset 2"));
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JKQTPBarVerticalGraph* graph3=new JKQTPBarVerticalGraph(&plot);
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graph3->setXColumn(columnX);
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graph3->setYColumn(columnY3);
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graph3->setTitle(QObject::tr("dataset 3"));
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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(graph3);
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// 6. now we set the graphs, so they are plotted side-by-side
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// This function searches all JKQTPBarVerticalGraph 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(0.75, 1);
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// 7. data is grouped into 5 numbere groups (1..5), but we also have string
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// labels for these groups (stored in L). In order to display these labels,
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// we have to tell the x-Axis to use these special labels:
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plot.getXAxis()->addAxisTickLabels(X, L, Ndata);
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// also we can rotate the labels a bit (by 45 degree), so they fit better
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plot.getXAxis()->setTickLabelAngle(45);
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plot.getXAxis()->setTickLabelFontSize(12);
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// 8. finally we move the plot key/legend to the outside, top-right
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// and lay it out as a single row
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// NOTE: plot is a descendent of QWidget, which uses an internal object of
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// type JKQTBasePlotter, which does the actual plotting.
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// So many properties of the plot are only available in this internal
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// object, which you can access by plot.getPlotter().
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plot.getPlotter()->setKeyPosition(JKQTPKeyOutsideTopRight);
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plot.getPlotter()->setKeyLayout(JKQTPKeyLayoutOneRow);
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// 9 autoscale the plot so the graph is contained
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plot.zoomToFit();
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// show plotter and make it a decent size
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plot.show();
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plot.resize(600,400);
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return app.exec();
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}
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```
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Note: Here we use the functions `JKQTPBarVerticalGraph::setXColumn()` and `JKQTPBarVerticalGraph::setYColumn()` to set the columns to use for the stack positions (X) and heights (Y). Instead you can also use the semantic version `JKQTPBarGraphBase::setBarPositionColumn()` and `JKQTPBarGraphBase::setBarHeightColumn()`.
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The result looks like this:
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In order to draw horizontal error bars, you have to use `JKQTPBarHorizontalGraph` instead of `JKQTPBarVerticalGraph`:
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