[R] Plots with discontinuity balls

[Paul Smith]

On 9/28/07, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
> >>> Can R plot graphs like the one at
> >>>
> >>> http://www.mathwords.com/f/f_assets/floor_graph.gif
> >>>
> >>> with the balls at the discontinuity points?
> >>>
> >> You can use segments() to draw the segments and symbols() to draw the
> >> balls.  For example,
> >>
> >> plot(1,1,type='n', xlim=c(1,10), ylim=c(1,10))
> >> segments(1:9, 1:9, 2:10, 1:9)
> >> symbols(2:10, 1:9, circles=rep(0.1,9), inches=FALSE, bg="white",add=T)
> >> symbols(1:9, 1:9, circles=rep(0.1,9), inches=FALSE, bg="black",add=T)
> >>
> >> This depends on the order of drawing, because the white background of
> >> the first circles obscures the ends of the segments.
> >>
> >
> > Thanks, Jim and Duncan. It would help to have transparent backgrounds
> > for the white balls.
> >
> Then it's even easier:  just use points(), with pch=1, e.g.
>
> plot(1,1,type='n', xlim=c(1,10), ylim=c(1,10))
> segments(1:9, 1:9, 2:10, 1:9)
> points(2:10, 1:9, pch=1, cex=2)
> points(1:9, 1:9, pch=16, cex=2)

Thanks, Duncan. That is a nice solution.

Paul