[R] screen resolution effects on graphics

[Prof Brian Ripley]

On Mon, 28 Aug 2006, Charles Annis, P.E. wrote:

> Greetings, R-Citizens:
> 
> I have the good fortune of working with a 19" 1280 X 1024 pixel monitor.  My

(Similar to our student lab has used for many years.)

> R-code produces nice-looking graphics on this machine but the same code
> results in crowded plots on an older machine with 800 X 600 resolution.  In
> hindsight this seems obvious, but I didn't anticipate it.

It is not obvious to me: I have never experienced it.  What OS and 
graphics device is this?

Almost all of R's graphics is independent of the screen resolution (the 
exception being the bitmapped devices such as jpeg), with things sized in 
inches or points. My machines are 1600x1200 (apart from 1280x800 on my 
laptop), so I meet a considerable reduction when using a computer 
projector, and my plots do not look crowded.

However, one issue is when the OS has a seriously incorrect setting for 
the screen resolution and so does not give the sizes asked for by R.  We 
have seen that on both Linux and Windows, and the windows() device has 
arguments to set the correct values.  (On X11 you should be able to set 
this in Xconfig files.)

If this is Windows, check carefully the description of the initial screen 
size in ?windows.  That can have unexpected effects on physically small 
screens.

At one time the X11() device was set up to assume 75dpi unless the 
reported resolution was 100+/-0.5dpi.  My then monitor reported 99.2 dpi 
and so things came out at 3/4 of the intended size.  We fixed that quite a 
while back.

> My code will be used on machines with varying graphics (and memory)
> capacity.  Is there a way I can check the native resolution of the machine
> so that I can make adjustments to my code for the possible limitations of
> the machine running it?

Only via C code, which is how R does it.

-- 
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