If you are always using asp=1 then you can just do something like: x <- rnorm(100, 1, 5) y <- rnorm(100, 3, 4)
plot( x,y, asp=1) r=2 nseg=360 x.cent <- 5 y.cent <- 7 xx <- x.cent + r*cos( seq(0,2*pi, length.out=nseg) ) yy <- y.cent + r*sin( seq(0,2*pi, length.out=nseg) ) lines(xx,yy, col='red') -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Allan Kamau > Sent: Saturday, March 12, 2011 1:08 PM > To: r-help@r-project.org > Subject: Re: [R] Drawing a circle on an existing graph. > > On Sat, Mar 12, 2011 at 10:22 PM, David Winsemius > <dwinsem...@comcast.net> wrote: > > > > On Mar 12, 2011, at 10:56 AM, Allan Kamau wrote: > > > >>> --- On Sat, 3/12/11, Allan Kamau <kamaual...@gmail.com> wrote: > >>> > >>>> From: Allan Kamau <kamaual...@gmail.com> > >>>> Subject: [R] Drawing a circle on an existing graph. > >>>> To: r-help@r-project.org > >>>> Received: Saturday, March 12, 2011, 3:08 AM > >>>> I would like to draw a circle on a > >>>> graph I am plotting in R and use > >>>> the current plot's coordinate system. > >>>> The most basic functionality I am looking for is the > >>>> ability to plot a > >>>> circle on an already existing graph by simply providing the > >>>> xy > >>>> coordinates for it's centre and the radius. > >>>> > >>>> I am also looking for a way to obtain x,y values of a point > >>>> (of a > >>>> circle) by specifying only the origin x,y the angle and > >>>> radius. > >>>> > >>>> Please point me so such a library and perhaps some simple > >>>> one line code. > >>>> > >>>> Allan. > >>>> > >> On Sat, Mar 12, 2011 at 5:28 PM, John Kane <jrkrid...@yahoo.ca> > wrote: > >>> > >>> Is this of any use? > >>> http://tolstoy.newcastle.edu.au/R/help/06/04/25821.html > >>> > >> > >> Thank you John, that is what I was looking for. > >> The code does draw a neat circle that is not stretched. After > plotting > >> the circle on an existing plot I notice that the original plot was > >> indeed stretched somehow by approximately some 1:1.1 ratio (I > think). > >> Now I am looking for a way to enforce none stretching in my original > >> graph. > > > > `plot.window` has an `asp` argument that is useful for that purpose. > Most > > plotting with base graphics will pass an asp=1 argument along as part > of the > > `...` arguments, > > > > -- > > > > David Winsemius, MD > > West Hartford, CT > > > > > Thank you David, asp=1 argument in my plot function brought about 1:1 > aspect ratio to the graph and now the circle sits very neatly within > it. All is well. > John is there another version of your circle drawing code that accepts > values in accordance with the current plot's scale units in place of > the current real distance measurement (inches) units. > > Allan. > > ______________________________________________ > R-help@r-project.org 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@r-project.org 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.
