gnuplot documentation

118 gnuplot 4.3 70 SET-SHOW
70.47 Parametric
The set parametric command changes the meaning of plot (splot) from normal functions to parametric
functions. The command unset parametric restores the plotting style to normal, single-valued
expression plotting.
Syntax:
set parametric
unset parametric
show parametric
For 2D plotting, a parametric function is determined by a pair of parametric functions operating on a
parameter. An example of a 2D parametric function would be plot sin(t),cos(t), which draws a circle
(if the aspect ratio is set correctly — see set size (p. 129)). gnuplot will display an error message if
both functions are not provided for a parametric plot.
For 3D plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v). Therefore a triplet of functions
is required. An example of a 3D parametric function would be cos(u)*cos(v),cos(u)*sin(v),sin(u),
which draws a sphere. gnuplot will display an error message if all three functions are not provided for
a parametric splot.
The total set of possible plots is a superset of the simple f(x) style plots, since the two functions can
describe the x and y values to be computed separately. In fact, plots of the type t,f(t) are equivalent to
those produced with f(x) because the x values are computed using the identity function. Similarly, 3D
plots of the type u,v,f(u,v) are equivalent to f(x,y).
Note that the order the parametric functions are specified is xfunction, yfunction (and zfunction) and
that each operates over the common parametric domain.
Also, the set parametric function implies a new range of values. Whereas the normal f(x) and f(x,y)
style plotting assume an xrange and yrange (and zrange), the parametric mode additionally specifies a
trange, urange, and vrange. These ranges may be set directly with set trange, set urange, and set
vrange, or by specifying the range on the plot or splot commands. Currently the default range for
these parametric variables is [-5:5]. Setting the ranges to something more meaningful is expected.
70.48 Plot
The show plot command shows the current plotting command as it results from the last plot and/or
splot and possible subsequent replot commands.
In addition, the show plot add2history command adds this current plot command into the history.
It is useful if you have used replot to add more curves to the current plot and you want to edit the
whole command now.
70.49 Pm3d
pm3d is an splot style for drawing palette-mapped 3d and 4d data as color/gray maps and surfaces. It
uses a pm3d algorithm which allows plotting gridded as well as non-gridded data without preprocessing,
even when the data scans do not have the same number of points.
Drawing of color surfaces is available on terminals supporting filled colored polygons with color mapping
specified by palette. Currently supported terminals include
Screen terminals:
OS/2 Presentation Manager
X11
Linux VGA (vgagl)
GGI
Windows
AquaTerm (Mac OS X)
wxWidgets (wxt)