milk: Daudin's Milk Composition Data

Description

Daudin et al.(1988) give 8 readings on the composition of 86 containers of milk. They speak about 85 observations, but this can be explained with the fact that observations 63 and 64 are identical (as noted by Rocke (1996)).

The data set was used for analysing the stability of principal component analysis by the bootstrap method. In the same context, but using high breakdown point robust PCA, these data were analysed by Todorov et al. (1994). Atkinson (1994) used these data for ilustration of the forward search algorithm for identifying of multiple outliers.

Usage

data(milk, package="robustbase")

Arguments

Format

A data frame with 86 observations on the following 8 variables, all but the first measure units in grams / liter.

X1: density
X2: fat content
X3: protein content
X4: casein content
X5: cheese dry substance measured in the factory
X6: cheese dry substance measured in the laboratory
X7: milk dry substance
X8: cheese product

References

Todorov, V., Neyko, N., Neytchev, P. (1994) Stability of High Breakdown Point Robust PCA, in Short Communications, COMPSTAT'94; Physica Verlag, Heidelberg.

Atkinson, A.C. (1994) Fast Very Robust Methods for the Detection of Multiple Outliers. J. Amer. Statist. Assoc. 89 1329--1339.

Rocke, D. M. and Woodruff, D. L. (1996) Identification of Outliers in Multivariate Data; J. Amer. Statist. Assoc. 91 (435), 1047--1061.

Examples

Run this code

# NOT RUN {
data(milk)
(c.milk <- covMcd(milk))
summarizeRobWeights(c.milk $ mcd.wt)# 19..20 outliers
umilk <- unique(milk) # dropping obs.64 (== obs.63)
summary(cumilk <- covMcd(umilk, nsamp = "deterministic")) # 20 outliers
# }
# NOT RUN {
<!-- %%not yet ## the best 'crit' we've seen was -->
# }