R plots pdf() does not allow spotcolors?

Matthieu Stigler <matthieu.stigler <at> gmail.com> writes:

Hi
We are about to publish a book, which contains figures made
with R plots. An important detail that we did not take into
account is that the book will not be printed in 4 colors
(cmyk mode), but only 2 (black +"spotcolor"). The spotcolor
we use is part of the big Pantone family.

The problem is that both pdf() and postscript() offer either
rgb or cmyk, but no spotcolors such as pantone. I'm afraid
this constraint can't be solved at all, and we can't use R
for creating these plots? I did not find any package that
would extend the colormodel to include spot colors... Did
anyone had a similar experience?

  Wasn't aware of spotcolors, but I bet you could hack the PDF
reasonably easily (if you have many figures you might have to
use awk/sed/perl ?) ... if you don't use R, what is your
alternative for creating the figures?

Ben Bolker

Don't expect to hack PDF "reasonably easily" -- for many reasons,
one of which is that in PDF different bits of a document can be
(and usually are) encapsulated in PDF "objects", whose physical
location in the PDF file can be pretty random (there is a kind
of "hash index" at the beginning which points to them). So a PDF
file can be heavily fragmented (as also can a PS file, though
usually not nearly so heavily). In theory it would be possible
for every single character in a textual document to be in a
separate "PDF object" and located in random order in the file!

As a general comment (which unfortunately doesn't address the
main problem raised by Matthieu), it can often be better to
use independent software to create figures/diagrams based on
numerical results computed by R. R's plots are quite nicely
done by default, but tweaking them to achieve a preferred
layout in R itself can be painfully time-consuming. Myself,
I farm this out to the 'pic' preprocessor in troff/groff,
using which any details whatever can be arranged exactly to
one's taste.

Since spotcolour printing is a multi-pass procedure, one can
prepare the separate "layers" in the respective colours, along
with any necessary crop-marks or "bulls-eyes", quite easily.

However, this too generates PS output in the first instance
(convertible to PDF of course), so suffers the same "binding"
to the RGB/CMYK colour paradigm. So Pantone would not be
available in the first instance (except insofar as a subset
of the Pantone "spectrum" corresponds to colours in CMYK).

However, I presume it is highly likely that there is software
which can take a file (PS or PDF) prepared using RGB/CMYK, and
convert this to a Pantone-compatible file.

Even so, this would depend on what your publisher/printer
requires in what you submit. It would be important to obtain
from them a full and exact specification of what they require
for colour printing in files submitted to them for printing.

Hoping this is of some help ...
Ted.

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E-Mail: (Ted Harding) <ted.harding at wlandres.net>
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Date: 13-Apr-11                                       Time: 14:17:56
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