[R] resolution (dpi) problem

[Prof Brian Ripley]

On Sat, 26 Apr 2008, Ted.Harding at manchester.ac.uk wrote:

> On 26-Apr-08 19:30:35, Chris Walker wrote:
>> I am using R 2.4.1 with Windows XP.
>>
>> I use the plot command in a fairly simple script and I use
>> the right mouse click on the plot and save as a postscript
>> file. I used the resultant file in a paper which was submitted
>> electronically. However, I get the following response from the
>> journal:
>>
>> Your manuscript has been unsubmitted because you failed to meet
>> the submission guidelines as indicated below:
>>
>> -Your figures must be submitted in TIFF or EPS format according
>> to the following minimum resolutions:
>>
>> 1200 dpi for black and white line art (simple bar graphs, charts,
>> etc.) 300dpi for halftones (black and white photographs) 600dpi
>> for combination halftones (Photographs that also contain line art
>> such as labeling or thin lines)
>>
>> Does anyone know how to produce the correct settings for the
>> journal (i.e.1200 dpi)?
>>
>> Thankyou
>> Chris W
>
> I'm about to swim in (for me) murky waters here, since I don't
> use R on Windows, so things may happen on that platform which
> I'm not aware of.
>
> But I just want to make general comments about PostScript and R.
>
> 1. R's postscript() device produces EPS, so that bit should
>   be satisfied.

Only if there is a single page in the file.  The help file says

    The postscript produced for a single R plot is EPS (_Encapsulated
    PostScript_) compatible, and can be included into other documents,

> 2. Normally, except when a graphic has been converted from a
>   bit-mapped format, a PostScript (or EPS) file does not
>   have any intrinsic resolution, so long as what it represents
>   is vector graphics (which includes the rendering of letters,
>   numerals, symbols, etc.). Any resolution applying to the
>   result when a PS/EPS file is displayed/printed depends on
>   the resolution of the "end device" (screen/printer etc.)
>   which does the rendering. In principle, PS/EPS has "infinite"
>   resolution (for instance, printing from EPS to photograpic film
>   using a laser beam could have resolution as fine as 100,000).

Actually, there is an intrinsic resolution since coordinates in the file 
are recorded to a finite accuracy.  In R's case this is 0.01 bp, that is 
7200 ppi (dpi is incorrect terminology for anything involving 
halftones).

> 3. It is of course possible that the software generating the
>   graphic implements certain things as bit-maps in the first
>   place, in which case what goes in the PS/EPS file will
>   inevitably do the same.

Possible in general, but not in R's postscript() device (which is what 
saving from the windows() menu uses).

> You do not say what sort of graphic you have plotted, so one
> cannot tell whether (3) applies. However, my feeling is that
> either the journal has got the wrong impression of what you
> sent them, or what was intended to be an EPS file in fact
> got created/converted to some other (bit-mapped) format
> before you extracted it and sent it off.
>
> Sorry not to be more specifically helpful, but I especially
> wanted to make points (1) and (2) above, for clarification.
>
> Best wishes,
> Ted.
>
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> E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 26-Apr-08                                       Time: 23:22:36
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-- 
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