2PLOT: plot caro, plot cross, plot dot, plot plus, plot square, plot triangle - draw markers

Usage: plot caro <x> <y>             (normal mode)
       plot cross <x> <y>
       plot dot <x> <y>
       plot plus <x> <y>
       plot square <x> <y>
       plot triangle <x> <y>

       plot caro [<x> <y1>...]       (list mode)
       plot cross [<x> <y1>...]
       plot dot [<x> <y1>...]
       plot plus [<x> <y1>...]
       plot square [<x> <y1>...]
       plot triangle [<x> <y1>...]

Normal mode: 
These commands mark the position (x,y) with the corresponding symbol. 
The size of the symbol is determined by the current value of the plot 
parameter marksize.

List mode: 
These commands mark the positions given by the vector expressions x,
y1,... with the corresponding symbol. If no vector expressions are
specified, all points of the list columns are marked. 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.