Parametric Plots

A parametric plot results from plotting a vector of two univariate expressions dependent on the same variable. In rectangular coordinates the value of the first expression is the x-coordinate, and the value of the second expression is the y-coordinate. In polar coordinates the value of the first expression is the radial distance from the origin. The value of the second expression is the angle, represented in either radians or degrees depending on the angle mode (see Angular Unit fieldAngular_Unit_field), and measured counterclockwise from the positive x-axis.

When plotting a parametric plot the 2D-plot window's Insert > Plot commandB2C2._ prompts you to enter information into the Parametric Plot ParametersParametric_Plot_Parameters dialog box.

When making a continuous parametric plot, the parameter interval is recursively subdivided until the curve can be accurately approximated by a straight line. This may take an unacceptably long time if subdividing the curve is outside the window or in the neighborhood of a singularity. If this occurs, use the Edit > Delete Plot command49KM2E to delete the continuous plot and replot the parametric expressions using the Parametric Plot ParametersParametric_Plot_Parameters dialog box to select discrete points.

Since parametric plots are done in a standard 2D-plot window, you can zoom, move the cross, and plot any mixture of expressions as described previously. Tracing a parametric plot works in the same way as tracing a polar plot (see Polar PlotsPolar_Plots).

The file 2D-plotExamples.dfw in the Users\Plotting directory includes several parametric expressions that are interesting to plot.

Functions for plotting parametrically defined space curves such as helixes are defined in the Graphics Functions.mthZG4ZTI utility file.