[R] Why are default sizes of plotting characters different?

[Deepayan Sarkar]

On Tuesday 14 January 2003 09:20 pm, Patrick Connolly wrote:
> I had occasion to use panel.superpose to draw points in a lattice
> plot, and chose to set the size to 1.1 using trellis.par.set().  I
> also wished to add some other plotting characters which I did with
> grid.points.  To get them looking like the same size as those done
> with panel.superpose, I needed to set the size to 0.8 using size =
> unit(.8, "char").  Now they end up looking quite similar even if not
> identical.
>
> Evidently, the default values have different bases.  What is the
> thinking behind those defaults?

The grid defaults are whatever Paul decided :) The defaults in lattice were 
chosen so that things look approximately similar to comparable Trellis plots 
in S-Plus. The precise definition in lattice is 

cex = 1 <==> size = unit(2.5, "mm")