[R] saving plots as objects?

Deepayan Sarkar deepayan at stat.wisc.edu
Fri Feb 27 08:50:19 CET 2004

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:


     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.


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