[R] transparent colors

[Prof Brian Ripley]

See ?rgb and the article by Paul Murrell in R-news 2004-2.  (The details 
of where it is supported have changed in the last three years, though.)

On Wed, 10 Oct 2007, Markus Loecher wrote:

> Dear R graphics experts,
> Do you know of any way of plotting semi-transparent points in R ?
> I face this problem any time I want to e.g. plot thousands of points
> that belong to two or three classes which I color code.
> With the default opaque colors, the plotting order matters and
> basically the points I plot last completely dominate the picture. I
> would much rather have the overlaying points mix in color..
>
> Thanks a lot,
> Markus

-- 
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