[R] Drawing rectangles in multiple panels

[Stephen Tucker]

In the Trellis approach, another way (I like) to deal with multiple pieces of
external data sources is to 'attach' them to panel functions through lexical
closures. For instance...

rectInfo <-
    list(matrix(runif(4), 2, 2),
         matrix(runif(4), 2, 2),
         matrix(runif(4), 2, 2))

panel.qrect <- function(rect.info) {
  function(x, y, ...) {
    ri <- rect.info[[packet.number()]]
    panel.rect(ri[1, 1], ri[1, 2], ri[2, 1], ri[2, 2],
               col = "grey86", border = NA)
    panel.xyplot(x, y, ...)
  }
}

xyplot(runif(30) ~ runif(30) | gl(3, 10),
       panel = panel.qrect(rectInfo))

...which may or may not be more convenient than passing rectInfo (and perhaps
other objects if desired) explicitly as an argument to xyplot().


--- Deepayan Sarkar <deepayan.sarkar at gmail.com> wrote:

> 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
> 
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