marker(shape, size, fill) selects a marker.
All arguments are optional.
shape must be one of + x - | o s d < > ^ v p h; see below.
size is specified in points.
fill is one of open|solid|brush|spine:
open — The mark is filled with white
solid — The mark is filled with the current pen's color
brush — The mark is filled with the current brush's color
spine — Draws lines from the center to the vertices of the chosen shape instead of drawing the shape.
The mark is always outlined with the current pen (which may be 'none', of course).
Marks are:
o : circle/disk
+ x : upright or diagonal crosses
- | : horizontal or vertical lines
s d p h : square, diamond, pentagon, or hexagon
< > ^ v : left / right / up / down pointing triangles
The fill style has no effect on + x - | marks.