We shall first consider plotting simple graphs showing the dependence of one variable upon another. Such a graph may be composed of several elements:

A box which defines the ranges of the variables, perhaps with axes and numeric labels along its edges.

A set of points or lines within the box showing the functional dependence.

A set of labels for the variables and a title for the graph.

In order to draw such a graph, it is necessary to call at least four of the PLplot functions:

`plinit`

, to initialize PLplot.`plenv`

, to define the range and scale of the graph, and draw labels, axes, etc.One or more calls to

`plline`

or`plpoin`

to draw lines or points as needed. Other more complex routines include`plbin`

and`plhist`

to draw histograms,`plerrx`

and`plerry`

to draw error-bars.`plend`

, to close the plot.

More than one graph can be drawn on a single set of axes by making repeated calls to the routines listed in item 3 above. PLplot only needs to be initialized once unless plotting to multiple output devices.