Ellipse containing percentage of given points in R

Question

I\'m drawing F1/F2 vowel graph (an example is here). Each vowel has several points/values, and I\'d like to draw an ellipse around the points, so that:

• ellipse

Answer 1

require(car)
 x=rnorm(100)
 y=1+.3*x+.3*rnorm(100)
 dataEllipse(x,y, levels=0.80)

So with your data:

with(olm ,dataEllipse(ol.f1, ol.f2, levels=0.8) )

Another package, mixtools, has similar capabilities but uses the alpha level rather than the 1-alpha:

 mu <- with(olm, c(mean(ol.f1), mean(ol.f2)) )
 sigma <- var(olm)  # returns a variance-covariance matrix.
 sigma
#          ol.f1     ol.f2
#ol.f1 1077.2098  865.9306
#ol.f2  865.9306 2090.2021

require(mixtools)
#Loading required package: mixtools
#Loading required package: boot
# And you get a warning that ellipse from car is masked.

ellipse(mu, sigma, alpha=0.2, npoints = 200, newplot = FALSE)

Which would overlay the earlier plot with the new estimate (which is slightly narrower in this case.