Prof Brian D Ripley
ripley at stats.ox.ac.uk
Wed Dec 13 21:55:25 CET 2000
On Thu, 14 Dec 2000, Paul Murrell wrote:
> > Random question to the R cognoscenti: is there a primitive accessible
> > through R code for drawing arcs and circles? Except for symbols(), all of
> > the circle- and ellipse-drawing code I've seen breaks the graphics into a
> > many-sided polygon ("edges" in piechart()). This doesn't matter for
> > bitmap graphics but for vector graphics it might sometimes be nice to have
> > access to such a function ...
> There is not a circle() function like there is a rect() function, but the
> symbols() function does use primitive circle drawing code rather than a
> polygon approximation (mostly**). So something like symbols(x=5, y=5,
> circle=5) draws a circle at position (5, 5). See help(symbols) for how to
> control the size of the circles. symbols() doesn't do arcs and may be
> inconvenient for general circle-drawing tasks so I think there is a good
> case for a circle() function.
Unfortunately, the `primitive' is for a circle and not an arc.
I suppose one could argue that from 1.2.0 it is accessible
through the .Call interface as the new Rgraphics.h exposes it as
/* Draw a circle, centred on (x,y) with radius r (in inches). */
void GCircle(double x, double y, int coords,
double radius, int col, int border, DevDesc *dd);
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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