[R] Getting rid of borders on semi-transparent plotting symbols

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Apr 22 21:07:26 CEST 2008

On Tue, 22 Apr 2008, Dieter Menne wrote:

> Karl Ove Hufthammer <Karl.Hufthammer <at> math.uib.no> writes:
>> R version 2.7.0 RC (2008-04-20 r45403)
>> When using semi-transparent filled plotting symbols, the border of the
>> symbol has a different (darker) colour than the interior:
>> plot(0, 0, pch=19, col="#FF000022")
> Same R version, Window, the problem turn up on-screen, but not when I do
> pdf()
> plot(0, 0, pch=19, col="#FF000022")
> dev.off()

This is subtle -- both devices are doing what they are documented to do. 
E.g. see p.538 of the PDF reference manual -- and BTW PDF viewers do not 
always follow the specification.  (That's not to say that they are doing 
what the graphics engine expects, because I cannot find that documented.
But then the first technical documentation of the device API is in the 'R 
Internals' manual for 2.7.0.)

But symbol 19 is asking to both stroke and fill the circle, and we first 
need to resolve if that is the intention.  I've asked the designer for 

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

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