OptionalshapeFill and outline of the markers. By default, both are the series' automatic color, and the outline is 0.75pt.
OptionalsizeMarker size in points (2-72).
OptionalsymbolThe symbol drawn at each point. auto gives each series its own symbol, in turn by series,
none draws no marker, and picture draws the picture set as the marker's fill.
A marker drawn at each point of a line, scatter, or radar series.