robustbase (version 0.5-0-1)

kootenay: (Modified) Waterflow Measurements of Kootenay River in Libby and Newgate

Description

The original data set is the waterflow in January of the Kootenay river, measured at two locations, namely, Libby (Montana) and Newgate (British Columbia) for 13 consecutive years, 1931--1943.

The data set is of mostly interest because it has been used as example in innumerous didactical situations about robust regression. To this end, one number (in observation 4) has been modified from the original data from originally 44.9 to 15.7 (here).

Usage

data(kootenay)

source

Original Data, p.58f of Ezekiel and Fox (1959), Methods of Correlation and Regression Analysis. Wiley, N.Y.

Details

Other modified versions of the data sets are also used in different places, see the examples below.

References

Hampel, F., Ronchetti, E., Rousseeuw, P. and Stahel, W. (1986) Robust Statistics: The Approach Based on Influence Functions; Wiley, N.Y.

Rousseeuw, P.~J. and Leroy, A.~M. (1987) Robust Regression & Outlier Detection, Wiley, N.~Y.

Examples

data(kootenay)
plot(kootenay, main = "'kootenay' data")
points(kootenay[4,], col = 2, cex =2, pch = 3)

abline(lm   (Newgate ~ Libby, data = kootenay), col = "pink")
abline(lmrob(Newgate ~ Libby, data = kootenay), col = "blue")

## The original version of Ezekiel & Fox:
kootenay0 <- kootenay
kootenay0[4, "Newgate"] <- 44.9
plot(kootenay0, main = "'kootenay0': the original data")
abline(lm   (Newgate ~ Libby, data = kootenay0), col = "pink")
abline(lmrob(Newgate ~ Libby, data = kootenay0), col = "blue")

## The version with "milder" outlier -- Hampel et al., p.310
kootenay2 <- kootenay0
kootenay2[4, "Libby"] <- 20.0 # instead of 77.6
plot(kootenay2, main = "The 'kootenay2' data",
     xlim = range(kootenay[,"Libby"]))
points(kootenay2[4,], col = 2, cex =2, pch = 3)
abline(lm   (Newgate ~ Libby, data = kootenay2), col = "pink")
abline(lmrob(Newgate ~ Libby, data = kootenay2), col = "blue")