2PLOT: plot shape - draw a shape enclosed by a Bezier spline curve

Usage: plot shape <x1> <y1> <x2> <y2> <x3> <y3> <x4> <y4> ... (normal mode)
       plot shape [[<x>] <y1>...]                             (list mode)

Normal mode: 
The command draws a shape enclosed by a Bezier spline curve defined by the 
given points. The total number of points must be 3n, with integer n>0. 

List mode:
The command draws shapes enclosed by Bezier spline curves through the points 
of the given vector expressions x, y1,... If no vector expressions are 
specified, splines are drawn through the points of all list columns. If the
x-expression is omitted (i.e. if only a single expression, y1, is given), the
x-coordinates are taken from the x-column of the list. The number of list 
points must be 3n, with integer n>0.