Creating a graph involves a variety of tasks, which thus can be
separated into components without significant additional costs.
This structure manifests itself also in the PyX source, where there
are different modules for the different tasks. They interact by some
well-defined interfaces. They certainly have to be completed and
stabilized in their details, but the basic structure came up in the
continuous development quite clearly. The basic parts of a graph are:
- graph
-
Defines the geometry of the graph by means of graph coordinates with
range [0:1]. Keeps lists of plotted data, axes etc.
- data
-
Produces or prepares data to be plotted in graphs.
- style
-
Performs the plotting of the data into the graph. It gets data,
converts them via the axes into graph coordinates and uses the graph
to finally plot the data with respect to the graph geometry methods.
- key
-
Responsible for the graph keys.
- axis
-
Creates axes for the graph, which take care of the mapping from data
values to graph coordinates. Because axes are also responsible for
creating ticks and labels, showing up in the graph themselves and
other things, this task is splitted into several independent
subtasks. Axes are discussed separately in chapter 5.
