# [R] Drawing a circle

Gabor Grothendieck ggrothendieck at gmail.com
Thu May 19 14:33:33 CEST 2005

```If a solid circle is ok then one can use the symbol pch=19
and blow it up using cex=, e.g.

plot(0, pch=19, cex=5, col="blue")

See balloonplot in package gplots for an example of this.

On 5/19/05, Chuck Cleland <ccleland at optonline.net> wrote:
> See ?symbols.  For example:
>
>  > a <- 1.975 # valore x del centro
>  > b <- 1.215 # valores y del centro
>  > r <- 1.460 # radio
>  > plot(0,0, type = "n", ylim=c(b - r, b + r), xlim=c(a - r, a + r))
>  > symbols(x = a, y = b, circles = r)
>
> Mario Morales wrote:
> > Hi.
> >
> > I need to draw a circle whit center (a,b) and radio r. So I use the
> > R code below
> >
> > a<-1.975 # valore x del centro
> > b<-1.215 # valores y del centro
> > x1<-seq(a-r,a+r,by=0.01); #los valores de x
> > yp<-sqrt(r^2-(x1-a)^2)+b; # los valores y a partir de la raíz positiva
> > yn<-(-1)*sqrt(r^2-(x1-a)^2)+b; # los valores y a partir de la raíz negativa
> > x<-c(x1,x1);  y<-c(yp,yn);
> >
> > plot(x,y,type="l",ylab="",xlab="",xlim=range(x),ylim=range(y));
> >
> >
> > My circle have two problems.
> >
> > First. I don't want the horizontal line and I don't know how avoid
> > it.
> >
> > Second. It is shaped like ellipse. I need adjust the x and y scales,
> > but I don't know how.
> >
> > Can you help me???
> >
> > there is another way to draw a circle whit R ?
> >
> > ______________________________________________
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> > https://stat.ethz.ch/mailman/listinfo/r-help
> > http://www.R-project.org/posting-guide.html
> >
> >
>
> --
> Chuck Cleland, Ph.D.
> NDRI, Inc.
> 71 West 23rd Street, 8th floor
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>
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