R-beta: image(x,y,z)?

[Ross Ihaka]

Bill Venables writes:
 > \begin{idleMusing}
 > Apropos of that, has any thought been given to implementing a
 > Tr*llis-style graphics system in R?  I presume the copyright
 > protection issues would be extreme (hence my paranoid caution in
 > not even mentioning full names...:-), but I do think the matter
 > is important.  I don't pretend to have a full answer to this one.
 > Tr*llis looks to me like about a decade's work, off an on, in the
 > planning and design stages and the result is wonderful.  The
 > designer should have full recognition of that and entitled to
 > copyright protection on his work, but if R is to be a modern
 > graphics system it has to have multi-paneled conditioning at
 > least.  Has anyone thought about graphics in R, perhaps with a
 > view to putting together a quite different scheme of high quality
 > graphics procedures?  Tr*llis may be excellent, but it does not
 > have to be unique.  I would even favour an entirely different
 > scheme that could stand as a real alternative to Tr*llis rather
 > than a simple immitator, but that is going to take real talent.
 > \end{idleMusing}

I have also come to the conclusion that the R graphics model has to
go.  It was a quick hack which was meant to fill a gap until the real
thing happened.  The present model is an imitation of the GRZ package
developed at Bell Labs before S came on the scene.  It is based on
arcane notions which are appropriate for pen plotters, but not modern
raster devices.

The major problem happens when graphics windows are resized.  To see
this have a look at
	> data(islands)
	> dotplot(islands)
Now reshape the graphics window.  The labels don't stay in the right
places.  This is because after a resize the "mar" and "mai" parameters
are in conflict.  (I have a band-aid for this particular problem, but
it a general one).

S gets around this by not allowing resizing of devices.  Yes, you can
reshape windows, but if you look at the device dimensions in inches
they never change.

At some point I would like to completely redo the graphics system in
the light of what I've learned from one of our PhD student's research
(and some of mny own tinkering).  But it won't happen for a while.  My
priority at present is to get something out which will be stable,
documented and useful for a reasonable subset of statistics.


As for trellis.  I don't really think that it is all that deep or
difficult.  It would be pretty easy to implement a passable "copy" and
there would be no legal problems provided that it was a clean room
implementation.  It's patents that create the real problem and as far
as I know there is no trellis patent (prior art can probably be traced
as far back as Decartes).

I even have a name.  How do you like "lattice". :-)

	Ross
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