Maximum number of bins, used when method is "histodot".
When method is "dotdensity", this specifies maximum bin width. When method is "histodot", this specifies bin width.
A boundary between two bins, used when method is "histodot".
The center of one of the bins, used when method is "histodot".
Use "dotdensity" for dot-density binning, or "histodot" for fixed bin widths (like in geomHistogram).