[Rd] graphics defaults

[Prof Brian Ripley]

On Fri, 14 Mar 2008, Deepayan Sarkar wrote:

> On 3/13/08, Ben Bolker <bolker at zoo.ufl.edu> wrote:
>>
>>    Can someone point me to a justification for the design
>>  decisions, which seem to be similar in lattice and
>>  ggplot2, of
>
> Disclaimer: I don't have strong personal preferences, I just went with
> what Trellis had. That said,
>
>> (1) gray backgrounds and
>
> lattice's default background is now white, and this was partly because
> many people seemed to dislike the grey background. My personal feeling
> is that it looked good on a screen or when using a beamer, but not so
> good when printed. ggplot's background is lighter, so this probably
> does not apply.

My memory is that Trellis had different schemes for different devices, so 
the background was white for plots intended for a printer.  Also, the 
default scheme for postscript() was 'black and white', and few people had 
colour printers.

Viewing conditions do matter here.  I remember that in 1992 Trellis' grey 
looked horribly dark and muddy on Bill Venables' Sun monitor, something we 
were able to alleviate by adjusting it.  But there is dissent about the 
gamma to be used on viewing screens and how dark a particular mid grey 
appears do depends on the gamma.  [Most use ca 2.2, Macs have always been 
different at 1.8, and I believe the SGI systems used at Bell Labs at the 
time Trellis was developed were different again.  Beamers (computer 
projectors) are often way off in their colour accuracy.]


>> (2) filled points?
>>  [I seem to remember seeing somewhere the opposite recommendation
>>  for points, i.e. that open points make it much easier to
>>  see if there are overlapping values -- and this would
>>  be a reason that pch=1 gives an open circle ...]
>
> lattice does have open circles by default, except in ungrouped dot
> plots, where there is no possibility of overlapping.

There are choices between 'open' and 'closed', and I find using 
translucent fills makes overlap easier to detect.  As from R 2.7.0 most 
graphics devices are capable of handling semi-transparent colours (at 
least on an opaque background, which is what is needed here).

-- 
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