[R] RFC: default background on lattice plots

[Prof Brian Ripley]

On Mon, 13 Mar 2006, Martin Maechler wrote:

>>>>>> "JohnF" == John Fox <jfox at mcmaster.ca>
>>>>>>     on Sat, 11 Mar 2006 13:29:34 -0500 writes:
>
>    JohnF> Dear Deepayan, As you say, it's currently very easy
>    JohnF> to change settings (which is what I do routinely),
>    JohnF> but since you asked, I much prefer the settings in
>    JohnF> canonical.theme("pdf") and therefore would prefer
>    JohnF> that the windows() device use these settings as a
>    JohnF> default (independent of the printing issue).
>
>    JohnF> Regards, and thanks for the lattice package,
>
> indeed, thanks a lot, Deepayan!
>
> I think it would make much sense to use the *same*  canonical.theme
> for all interactive default devices.
> This may be important in teaching, packages, user-written
> functions which often are all meant to be used interactively; I
> think it would be painful if students in my class looked at
> quite differently colored pictures depending on if they are
> using MacOS X, Linux or Windows.
>
> Hence, if you change the setting for windows(), I think you
> should also do so for  x11() and quartz().

That would be an even stronger argument if those devices all rendered RGB 
colours the same, but MacOS is running a different default interpretation, 
AFAIK (and many PC displays are still way off sRGB, hence the gamma 
argument of some devices but unfortunately not quartz()).  Beyond that, 
the visual effect is dependent both on the brilliance setting of the 
display and ambient lighting levels, and most people have screens set far 
too bright (and work in too harshly lit environments) to achieve optimal 
rendition.

I can see two defensible positions.

1) Default themes are chosen for each device with a common 'perceptual 
intent' (a technical phrase).  I believe that was the aim of Trellis, but 
one not achieved on many displays (I remember a muddy brown background on 
an old Sun display Bill Venables had).

2) The same theme is chosen for all devices, and the user is expected to 
establish proper viewing conditions.  That would mean using the same 
default theme for _all_ devices.

I think 2) has to be the way forward, as nowadays there is no reason to 
suppose that postscript() or pdf() output will be printed rather than say 
included into a lecture presentation (and if so whether that will be 
printed or 'beamed').

(Ross Ihaka did once mention an intent to include colour management into 
R, so that R RGB colours were rendered as accurately as possible in sRGB. 
That would remove the MacOS anomaly.)

-- 
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