[R] Drawing rectangles in multiple panels

[Deepayan Sarkar]

On 7/11/07, hadley wickham <h.wickham at gmail.com> wrote:
> > A question/comment: I have usually found that the subscripts argument is
> > what I need when passing *external* information into the panel function, for
> > example, when I wish to add results from a fit done external to the trellis
> > call. Fits[subscripts] gives me the fits (or whatever) I want to plot for
> > each panel. It is not clear to me how the panel layout information from
> > panel.number(), etc. would be helpful here instead. Am I correct? -- or is
> > there a smarter way to do this that I've missed?
>
> This is one of things that I think ggplot does better - it's much
> easier to plot multiple data sources.  I don't have many examples of
> this yet, but the final example on
> http://had.co.nz/ggplot2/geom_abline.html illustrates the basic idea.

That's probably true. The Trellis approach is to define a plot by
"data source" + "type of plot", whereas the ggplot approach (if I
understand correctly) is to create a specification for the display
(incrementally?) and then render it. Since the specification can be
very general, the approach is very flexible. The downside is that you
need to learn the language.

On a philosophical note, I think the apparent limitations of Trellis
in some (not all) cases is just due to the artificial importance given
to data frames as the one true container for data. Now that we have
proper multiple dispatch in S4, we can write methods that behave like
traditional Trellis calls but work with more complex data structures.
We have tried this in one bioconductor package (flowViz) with
encouraging results.

-Deepayan