[R] Is something wrong wiht draw.circle()?

[William Dunlap]

Add asp=1 to your call to plot() to force equal scales on both axes.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Peter Langfelder
> Sent: Friday, September 07, 2012 10:03 AM
> To: Chris82
> Cc: r-help at r-project.org
> Subject: Re: [R] Is something wrong wiht draw.circle()?
> 
> On Fri, Sep 7, 2012 at 9:04 AM, Chris82 <rubenbauar at gmx.de> wrote:
> > Hey R users,
> >
> > I am a little bit confused.
> >
> >
> > require(plotrix)
> >
> > plot(0,xlim=c(-10,10),ylim=c(-10,10),type="n",xlab="",ylab="")
> > draw.circle(0,0,5)
> >
> > lines(c(0,0),c(0,5))
> > lines(c(0,5),c(0,0))
> 
> The culprit are unequal margins. Issue
> 
> par(mar = c(4,4,4,4))
> 
> before your code, and you will get a consistent circle.
> 
> More generally, when the scale of x axis and y axis are not the same
> (i.e., 1 unit corresponds to different distances __on screen__),
> drawing a naive circle would result in something that looks like an
> ellipse on screen. Plotrix can apparently draw a real circle but then
> the radius is "correct" only in the x direction.
> 
> HTH,
> 
> Peter
> 
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