Graphs

Collaboration diagram for Graphs:

Graph Class Structure

Each type of graph is represented by another class, which has to be derived from JKQTPPlotElement. This class provides a basic virtual interface that allows JKQTPlotter to draw the graphs represented by them. This interface consists of these functions:

• JKQTPPlotElement::draw() draws the graph onto a given JKQTPEnhancedPainter (derived from QPainter)
• JKQTPPlotElement::drawKeyMarker() draws the small marker image in the plot legend
• JKQTPPlotElement::getKeyLabelColor() returns a color for the legend entry for the graph
• JKQTPPlotElement::getXMinMax() returns the extent of the graph in x-direction (e.g. for auto-zooming)
• JKQTPPlotElement::getYMinMax() returns the extent of the graph in Y-direction (e.g. for auto-zooming)

In addition to these basic functions, there are additional functions that can be used to draw something outside the actual plot rectangle. These are used to e.g. add color-scales to the side of the graph:

• JKQTPPlotElement::getOutsideSize() returns the amount of space required outside the plot rectangle
• JKQTPPlotElement::drawOutside() draws the elements outside the plot rectangle

Usually if writing a new graph, one would not directly derive from JKQTPPlotElement, but from a cass in it's hirarchy of children. These children already provide certain facilities for certain types of graphs.

Mix-In Classes for Graphs

See also

Mix-in classes for Graphs

In addition there are mix-in classes that are used via multiple inheritance that add additional features and properties to a graph. A prominent example are the classes for error indicators. With these there are usually two variants of one type of graph: One without error indicators and one with error indicators, e.g.:

• JKQTPXYLineGraph shows lines+symbols graphs made up from x/y-value pairs for each data point.
• JKQTPXYLineErrorGraph extends JKQTPXYLineGraph with error indicator drawing/properties provided by JKQTPXYGraphErrors

This approach allows to keep interfaces and appearance recognizeable over different graph classes and locates the source code for a feature like error indicators in a single/in few class(es).

Another example of such a class is JKQTPColorPaletteStyleAndToolsMixin, which provides functions that allow to use color palettes. It is mainly used for the Image/Matrix graphs, but also by e.g. JKQTPXYParametrizedScatterGraph.