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 > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >