[R] saving plots as objects?

[Prof Brian Ripley]

On Fri, 27 Feb 2004, Deepayan Sarkar wrote:

> On Friday 27 February 2004 01:22, Prof Brian Ripley wrote:
> > On Thu, 26 Feb 2004, Deepayan Sarkar wrote:
> > > On Thursday 26 February 2004 14:47, Rajarshi Guha wrote:
> > > > Hi I had two questions regarding plots:
> > > >
> > > > * Is there are way to save a plot in the form of an object such that
> > > > it could be displayed/modified later?
> > >
> > > Depends on what you want to do. Probably not for regular (base) plots.
> >
> > I think ?recordPlot does this, at least to allow plots to be saved,
> > displayed again and added to.
> 
> Ah, I didn't know that.
> 
> > > The
> > > grid package has a concept of objects that can be edited (before
> > > and/or after plotting them). Functions in the lattice package produce
> > > objects that may be close to what you want. They are not plots
> > > themselves, but rather a self-contained description of a plot (in the
> > > sense that they contain the data as well as instructions on how to
> > > plot it). The data part cannot be easily changed, but almost
> > > everything else can be manipulated before plotting.
> >
> > AFAIK that internal description is not documented and there are no
> > end-user tools for doing the manipulation.  Can you please point us to
> > details?   I suspect nothing can _easily_ be changed by end-users at
> > present.
> 
> 
> There has always been an update() method that's supposed to be used for 
> this. No one uses it much, and it probably has a few bugs (but should be 
> improved in time for R 1.9.0). From ?xyplot:
> 
> Value:
> 
>      An object of class ``trellis''. The `update' method can be used to
>      update components of the object and the `print' method (usually
>      called by default) will plot it on an appropriate plotting device.

Ah, I see.  It cannot change the panel function, for example, indeed none 
of the things I was thinking about.  I had thought update() recalculated 
the plot, so I've learned something, thank you.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595