[R] ploting an ellipse keeps giving errors

[John Fox]

Dear Sun,

There are indeed (at least) two ellipse functions, and the one in the car
package has different arguments from the one in the ellipse package.

You should be able to use ellipse() in either package to do what you want;
use the t argument for the version in ellipse or the radius argument for the
version in car, setting this to the square-root of the critical chisquare or
F. (ellipse in car works by deforming a circle.) If height and weight are
from the same sample, then they won't be independent, so, e.g., the shape
argument to ellipse in car would be their sample covariance matrix. The
center argument to ellipse() in car and the centre argument to ellipse() in
ellipse should be the vector of means.

But the ellipse() function in ellipse and the data.ellipse() function in car
already does all this, so why do you feel that you need to roll your own (or
perhaps I misunderstand what you want)? 

I hope this helps.
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Sun
> Sent: Wednesday, October 27, 2004 4:25 AM
> To: Petr Pikal
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] ploting an ellipse keeps giving errors
> 
> Thank you. I found there are two ellipses
> 
> 1.
> R2.0
> library (car)
> 
> 2.
> R1.9 and R2.0
> library (ellipse)
> 
> And they are different! I can't run 1.
> 
> But the 2. is kind of specialized for t-distribution 
> confidence and so on.
> 
> I need to find a general ellipse for an ellipse equation like 
> (x-x0)^2/a + (y-y0)^2/b =1
> 
> . Since I used chi-square percentile not t. I am trying to 
> obtain the large sample 95% simultaneous confidence ellipse 
> for two population means (say, weight and height). The input 
> are the two sample means and their covariances.
> 
> Maybe I have to make my own ellipse function.
> 
> Sun
> ----- Original Message -----
> From: "Petr Pikal" <petr.pikal at precheza.cz>
> To: "Sun" <sun at cae.wisc.edu>
> Cc: <r-help at stat.math.ethz.ch>
> Sent: Wednesday, October 27, 2004 4:14 AM
> Subject: Re: [R] ploting an ellipse keeps giving errors
> 
> 
> > Hi
> >
> > Did you read what ellipse does and how it shall be used?
> >
> > And what about your system, R and ellipse version?
> >
> > From your example i got
> >
> > > ellipse (center = c(0,0), shape = shape1, radius = 1)
> > Error in ellipse.default(center = c(0, 0), shape = shape1, radius =
> > 1) :
> >         Argument "x" is missing, with no default
> >
> > Ellipse is not for drawing arbitrary ellipses but has 
> different usage.
> >
> > See its help page and an example.
> >
> > Cheers
> > Petr
> >
> >
> >
> >
> > On 27 Oct 2004 at 3:34, Sun wrote:
> >
> > >
> > > library (ellipse)
> > >
> > > shape1 = c (1, 0, 0,1)
> > > dim(shape1) = c(2,2)
> > > ellipse (center = c(0,0), shape = shape1, radius = 1)
> > >
> > > =============================
> > > Error in plot.xy(xy.coords(x, y), type = type, col = col, 
> lty = lty,
> > > ...) :
> > >         plot.new has not been called yet
> > >
> > >
> > > It is really frustrating. Also what do the shape matrix, radius
> > > correspond to an ellipse function
> > >
> > > (x-x0)^2/a + (y-y0)^2/b = 1
> > >
> > > ? Please advise!
> > >
> > > Many thanks,
> > >
> > > Sun
> > >  [[alternative HTML version deleted]]
> > >
> > > ______________________________________________
> > > R-help at 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
> >
> > Petr Pikal
> > petr.pikal at precheza.cz
> >
> >
> >
> 
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