Usage of JKQTPlotter Widget

Collaboration diagram for Usage of JKQTPlotter Widget:

JKQTPlotter is a plotter widget which wraps around a JKQTBasePlotter instanced that does the actual drawing. A basic usage of JKQTPlotter looks like this:

// create a new JKQTPlotter instance
JKQTPlotter* plot = new JKQTPlotter(parentWidget);
 
// fill two vectors with dtaa for a graph:
QVector<double> X, Y;
fillDataVectors(X, Y);
 
// make data available to the internal datastore of the plotter:
size_t columnX=plot->getDatastore()->addCopiedColumn(X, "x");
size_t columnY=plot->getDatastore()->addCopiedColumn(Y, "y");
 
// create a graph/curve, which displays the data
JKQTPXYLineGraph* graph1=new JKQTPXYLineGraph(plot);
graph1->setXColumn(columnX);
graph1->setYColumn(columnY);
graph1->setTitle(QObject::tr("graph title"));
plot->addGraph(graph1);
 
// autoscale the plot
plot->zoomToFit();
// alternatively set the axis dimension by hand:
plot->setXY(-10,10,-10,10);

The result should look something like this:

Starting from this basic example, you can observe several important principles:

1. Data is stored in an (internal) instance of JKQTPDatastore, which is accessible through JKQTPlotter::getDatastore(). This datastore can either own its data (which is done here, as we copy the data into the store by calling JKQTPDatastore::addCopiedColumn(), or it can merely reference to the data (then data needs to be available as array of double values).
2. Naming conventions (excerpt from Conventions: Naming and Plot Construction ):
   • plot is the complete drawn image, including the axes, the graphs, the key and all other visual elements
   • plot element any sub element of the plot, e.g. a single coordinate axis, the key, but also any graph/curve
   • graph is a single curve/image/geometric element in the plot
   • geometric element is a special graph that does not represent a curve based on data from the JKQTPDatastore, but a single graphic element, like a rectangle/circle/line/..., some text, a single symbol
   • key is the legend of the plot
   • coordinate axis is each of the x- or y-axis (there might be addition axes, e.g. when showing a color-scale)
3. Each graph is represented by a class derived from JKQTPPlotElement (in the example we instanciated a JKQTPXYLineGraph, which shows data as a scatter of symbols that may (or may not) be connected by a line). Creating the graph class does not yet add it to the plotter. To add it, call JKQTPlotter::addGraph(). Only after this sep, the graph is displayed. You can modify the apperance of the graph (e.g. colors, name in the key ...) by setting properties in the graph class instance.
4. You can auto-zoom the axis ranges of the plot by calling JKQTPlotter::zoomToFit(), or set them exlicitly by calling JKQTPlotter::setXY(). The user can later zoom in/out by the mouse (and other means). You can limit this zoom range by setting an absolute axis range, calling e.g. JKQTPlotter::setAbsoluteXY(). The the user cannot zoom farther out than the given range(s).
5. If you want to style the plot itself, you need to set properties of the underlying JKQTBasePloter instance, which is accessible through JKQTPlotter::getPlotter(). If you want to style the coordinate axes, you can acces their representing objects by caling JKQTPlotter::getXAxis() or JKQTPlotter::getYAxis().

See also

Example (JKQTPlotter): Very simple line-graph and

JKQTPlotterQtCreator