7 Plotting

The Plot component ( Display Plot ) displays graphical representations of real and composite expressions.

The graph of a real expression shows how the value of the expression varies as a variable in the expression varies. The display is generated by considering a real expression as a function, evaluating it at various points and drawing line segments between those points. (see §7.2).

Composite expressions are interpreted as point values. Individual point values are interpreted as position vectors. Sequences of point values are interpreted as line segments. See §7.3 and §7.6.

Real and point variables are represented as active points on the display. A real variable is displayed as a cursor along the X-axis. Point variables are displayed as cursors in X-Y space. Both types of cursor can be dragged. Other expressions dependent on the variables are redisplayed with the new values.

In a limited way, 3-dimensional point sequences can also be rendered to two dimensions. See §7.9.

Because some expressions refer to other (definition) expressions, references must be resolved before an expression can be plotted. For resolution to succeed, referenced expressions must be added to the plotter. These expressions can be marked as “hidden” so they are not themselves plotted. Refer to §9.2 for an advanced description of references and binding.