Re: [R] Drawing rectangles in multiple panels

From: Deepayan Sarkar <deepayan.sarkar_at_gmail.com>
Date: Sat, 14 Jul 2007 18:32:25 -0700

On 7/14/07, Stephen Tucker <brown_emu_at_yahoo.com> wrote:
>
> I wonder what kind of objects? Are there large advantages for allowing
> lattice functions to operate on objects other than data frames - I
> couldn't find any screenshots of flowViz but I imagine those objects
> would probably be list of arrays and such? I tend to think of mapply()
> [and more recently melt()], etc. could always be applied beforehand,
> but I suppose that would undermine the case for having generic
> functions to support the rich collection of object classes in R...

There's a copy of a presentation at

http://www.ficcs.org/meetings/ficcs3/presentations/DeepayanSarkar-flowviz.pdf

and a (largish - 37M) vignette linked from

http://bioconductor.org/packages/2.1/bioc/html/flowViz.html

Neither of these really talk about the challenge posed by the size of the data. The data structure, as with most microarray-type experiments, is like a data frame, except that the response for every experimental unit is itself a large matrix. If we represented the GvHD data set (the one used in the examples) as a "long format" data frame that lattice would understand, it would have 585644 rows and 12 columns (8 measurements that are different for each row, and 4 phenotypic variables that are the same for all rows coming from a single sample). And this is for a smallish subset of the actual experiment.

In practice, the data are stored in an environment to prevent unnecessary copying, and panel functions only access one data matrix at a time.

-Deepayan

> --- Deepayan Sarkar <deepayan.sarkar@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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