[R] calculating area of ellipse

[John Fox]

Dear James,

To mix notation a bit, presumably the (border of the) confidence ellipse 
is of the form (b - beta)'V(b)^-1 (b - beta) = c, where V(b) is the 
covariance matrix of b and c is a constant. Then the area of the ellipse 
is pi*c^2*sqrt(det(V(b))). It shouldn't be hard to translate that into R 
code.

I hope this helps,
  John

John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
web: https://socialsciences.mcmaster.ca/jfox/

John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
web: https://socialsciences.mcmaster.ca/jfox/

On 2021-05-06 7:24 a.m., james meyer wrote:
> In doing meta-analysis of diagnostic accuracy I produce ellipses of confidence
> and prediction intervals in two dimensions.  How can I calculate the area of
> the ellipse in ggplot2 or base R?
> 
> thank you
> James Meyer
> 
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