[R] Drawing a circle on an existing graph.

[John Kane]

Sorry Alan but it's not my function.  I just was looking for something similar a while ago and googled to find The
ost whose url I sent you will have the name of the creator.

Actually I think I ended up just using symbols for my graph.
--- On Sat, 3/12/11, Allan Kamau <kamauallan at gmail.com> wrote:

> From: Allan Kamau <kamauallan at gmail.com>
> Subject: Re: [R] Drawing a circle on an existing graph.
> To: r-help at r-project.org
> Received: Saturday, March 12, 2011, 3:07 PM
> On Sat, Mar 12, 2011 at 10:22 PM,
> David Winsemius
> <dwinsemius at comcast.net>
> wrote:
> >
> > On Mar 12, 2011, at 10:56 AM, Allan Kamau wrote:
> >
> >>> --- On Sat, 3/12/11, Allan Kamau <kamauallan at gmail.com>
> wrote:
> >>>
> >>>> From: Allan Kamau <kamauallan at gmail.com>
> >>>> Subject: [R] Drawing a circle on an
> existing graph.
> >>>> To: r-help at 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 <jrkrideau at 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.
> 
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