Here is an approach that clips the circle you like from symbols down to an arc (this will work as long as the arc is less than half a circle, for arcs greater than half a circle, you could draw the whole circle then use this to draw an arc of the bacground color over the section you don't want):
library(TeachingDemos) plot(-5:5, -5:5, type='n') clipplot( symbols(0,0,circles=2, add=TRUE), c(0,5), c(0,5) ) Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [EMAIL PROTECTED] (801) 408-8111 > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Paulo Barata > Sent: Monday, April 30, 2007 8:17 PM > To: r-help@stat.math.ethz.ch > Subject: [R] to draw a smooth arc > > > Dear R-list members, > > I would like to draw a smooth arc. I can draw an arc > parametrically, but this produces an arc too coarse, even > allowing for different increments in sequence t in the > example below. Function "symbols" (graphics) does produce a > smooth circle, but it cannot produce an arc. > > Please see the following example, drawing complete circles: > > plot(-5:5,-5:5,type='n') > ## draws circle with function symbols (package graphics) ## - > inner circle is very smooth: > symbols(0,0,circles=2,add=TRUE) > ## draws circle parametrically - outer circle is too coarse: > pi <- 4*atan(1) > t <- seq(0,2*pi,0.02) > lines(4*cos(t),4*sin(t)) > > Package "plotrix" has a function "draw.arc", but arcs > produced with this function are also either too coarse or too > polygonal, depending on the number of polygons used to > approximate the arc. > > Is there a way to harness the characteristics of function > "symbols" (graphics) to draw a smooth arc, not just a complete circle? > > I am using R 2.5.0, running under Windows XP. > > Thank you very much. > > Paulo Barata > > ----------------------------------------------------------------- > Paulo Barata > Fundacao Oswaldo Cruz (Oswaldo Cruz Foundation) Rua Leopoldo > Bulhoes 1480 - 8A 21041-210 Rio de Janeiro - RJ Brazil > E-mail: [EMAIL PROTECTED] > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.