STAR: Set this flag to get a star. E.g.,
vsym, 5,/star gets you a pentagram.
SKELETON: Set this flag to get an asterisk-like symbol, where
the center is connected to each vertex. E.g.,
vsym, 4, /skel gets you an X.
POLYGON: Set this flag to get a regular polygon. This is
the default symbol type.
FILL: Set this flag to get filled symbol. Default=open
ROT: Rotation of symbol about center, in degrees.
E.g., vsym, 4, rot=45 gets you a diamond, whereas
vsym, 4 gets you a square.
THICK: Line thickness of symbol. Default=!P.thick