[R] Exporting graphics to PS or EPS

[Prof Brian D Ripley]

On Sat, 19 Aug 2000, Joel West wrote:

> On Fri, 18 Aug 2000 07:49:44 +0100, Brian D Ripley <ripley at stats.ox.ac.uk> wrote:
> >On Thu, 17 Aug 2000, Paul E Johnson wrote:
> >> My experience is that, if I output a gif that does not
> >> fit on the page, then I've shot myself in the foot because resizing the
> >> graph makes all the text in it too small.  I don't think postscript is
> >> immune to this problem, but you can for sure convince me I'm wrong.  I
> 
> >It is.  After all, my books on S are done that way, as is much professional
> >publishing.    If you want to incorporate graphs into other documents (not,
> >say, a Web site) use a re-scalable vector format, namely postscript, PDF or
> > (on Windows) W/EMF.
> 
> To second Prof. Ripley, the point of PostScript is that is a device-independent, resolution-independent page description language.
> 
> On Fri, 18 Aug 2000 10:36:53 -0400, Griffith Feeney <gfeeney at hawaii.edu> wrote:
> >I don't have much experience with this, but I think you may want eps for 
> >use in TeX documents. You might want to have a look at
> 
> You absolutely want to use EPSF or instead of PS for any graphic that 
you are going to paste into another document. That's the whole point. 
Raw PostScript is write-only and really only usable for immediate 
downloading to a printer or RIP.

(Not if it is DSC-conformant: see below.  Then it is designed to be sent to
a document manager for page-by-page manipulation.)

> EPSF provides additional context around the PostScript job so that it 
can be placed, and resized by programs that do not include a 
PostScript interpreter. It also includes a low-res bit image so that 
you can view the image on screen during editing. For a description of 
EPSF and various other vector and bitmap formats, see the 
Encyclopedia of Graphics File Formats from O'Reilly at
> 	http://www.oreilly.com/catalog/gffcd/

The preview image is only required in EPSI (I for Interchange) files.  See
the definitive source, the PostScript Language Reference Manual from Adobe.
The critical point about EPSF is that it bans some of the PS operators, and
unfortunately R (up to and including 1.1.1) got that slightly wrong. What
you are describing is DSC-conformance, and R does manage that.

> PDF was developed in the mid-90s as an editable prepress exchange 
version of PostScript. (That's why it's going to be the native 
graphics format for Mac OS X). A pretty good discussion of how it 
works can be found online at
> 	http://www.seyboldseminars.com/News/Front/PDFday.html
> An added benefit of PDF over EPSF is that there is a free viewer 
program from Adobe for Windows, Mac, and some of the major flavors of Unix.

ghostscript/ghostview/gv/GSView are more widely available, and "free" in
the R sense (Open Source) not just `no cost'.  The only `some of the major
flavors of Unix' is a big drawback for Acrobat Reader, as is its bugginess,
especially on Linux (and as frequently reported on the pdftex list) the
Mac.  These days ghostscript does a pretty good job with PDF.
 
> Generating PDF is harder than EPSF, but it would be a nice 
extension to R someday.

Take a look at help(bitmap): it is already there.  One day we will write a
direct PDF graphics device, but having an indirect one has lowered its
priority.   (Notice I did mention PDF as an alternative.)

-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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