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Geological Society, London, Special Publications; 2006; v. 264; p. 191-201;
DOI: 10.1144/GSL.SP.2006.264.01.14
© 2006 Geological Society of London

General Theory and Methods

Rounded zeros: some practical aspects for compositional data

J. A. Martín-Fernández & S. Thió-Henestrosa

Departament Informàtica i Matemàtica Aplicada, Universitat de Girona, Campus Montilivi, Edifici P-IV, E-17071, Girona, Spain

(e-mail: josepantoni.martin{at}udg.es)

It is very important to realize that the well-known ‘zeros problem’ in compositional data is inherent in the nature of the data rather than in the log-ratio methodology. In a strict sense, any null value is informative itself and needs specific treatment before a multivariate method is applied. In the rounded zero case specific techniques of missing data should be applied as a previous step, taking into account that any of these techniques must respect the compositional nature of the data. In practice, when an imputation method is applied, then it is necessary to make a sensitivity analysis of the results from multivariate analysis. These methodological aspects are applied and illustrated using compositional data from geological samples.





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[Abstract] [PDF]