[R] Drawing rectangles in multiple panels

Stephen Tucker brown_emu at yahoo.com
Thu Jul 12 04:15:59 CEST 2007

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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