rrcov (version 0.3-07)

brain: Brain and Body Weights for 28 Species

Description

Average brain and body weights for 28 species of land animals. If the log of the two variables, i.e. log(brain weight) and log(body weight) are taken, the classical Mahalanobis distance declares only observation 25 (Brachiosaurus) as an outlier, whereas the robust distances computed using for example MCD - covMcd() - declare four observations as outliers (25, 6, 14 and 16). These are three dinosaurs with relatively small brains and the human with relatively heavy brain.

Usage

data(brain)

source

P. J. Rousseeuw and A. M. Leroy (1987) Robust Regression and Outlier Detection. Wiley, p.57.

Examples

data(brain)
lbrain<-log(brain)
plot(mahalanobis(lbrain,mean(lbrain),var(lbrain)))

mcd<-covMcd(lbrain)
plot(mahalanobis(lbrain,mcd$center,mcd$cov))