oliveoil {pdfCluster}R Documentation

Olive oil data

Description

This data set represents eight chemical measurements on different specimen of olive oil produced in various regions in Italy (northern Apulia, southern Apulia, Calabria, Sicily, inland Sardinia and coast Sardinia, eastern and western Liguria, Umbria) and further classifiable into three macro-areas: Centre-North, South, Sardinia. The data set is used to evaluate the pdfCluster ability of recunstructing the macro-area membership.

Usage

data(oliveoil)

Format

This data frame contains 572 rows, each corresponding to a different specimen of olive oil, and 10 columns. The first and the second column correspond to the macro-area and the region of origin of the olive oils respectively (here, the term "region" refers to a geographical area and not to administrative borders); Columns 3-10 represent the following 8 chemical measurements on the acid components for the different specimen of oil: palmitic, palmitoleic, stearic, oleic, linoleic, linolenic, arachidic, eicosenoic.

Details

Since the raw data are of compositional nature, ideally totalling 10000, some preliminary transformations of data are advisable. In particular, Azzalini and Torelli (2007) adopt an additive log-ratio transformation (ALR). Denoted as x_j, j=1,…,8 the j^{th} chemical measurement, the ALR transformation is y_j= \log x_j/x_k, j\neq k, where k is an arbitrary but fixed variable. However, in this data set, the raw data do not always sum up exactly to 10000, because of measurement errors. Moreover, some 0s are present in the data, corresponding to measurements below the instrument sensitivity level. Therefore, it is suggested to add 1 to all raw data and normalize them by dividing each entry by the corresponding row sum ∑_j (x_j+1).

Source

Forina, M., Lanteri, S. Armanino, C., Casolino, C., Casale, M., Oliveri, P. (2008). V-PARVUS. An Extendible Pachage of programs for esplorative data analysis, classification and regression analysis. Dip. Chimica e Tecnologie Farmaceutiche ed Alimentari, Università di Genova. Freely available at http://www.parvus.unige.it.

References

Forina M., Armanino, C., Lanteri, S., Tiscornia, E. (1983) Classification of olive oils from their fatty acid composition. In: Martens, M., Russwurm, H. Jr. (eds). Food Research and data Analysis, Applied Science Publishers, London, 189-214.


[Package pdfCluster version 1.0-0 Index]