an:05215478
Zbl 1130.86001
Palarea-Albaladejo, Javier; Martín-Fernández, Josep A.; Gómez-García, Juan
A parametric approach for dealing with compositional rounded zeros
EN
Math. Geol. 39, No. 7, 625-645 (2007).
0882-8121 1573-8868
2007
j
86-08 86A32 62H30 65C60
Additive log-ratio transformation; Compositional data; EM algorithm; Simplex
Summary: In this work, a parametric approach for replacing data below the detection limit, also known as rounded zeros, in compositional data sets is proposed. Compositional rounded zeros correspond to small proportions of some whole that cannot be reliably detected by the analytical instruments under given operating conditions. This kind of zeros appear frequently in the data collection process in geosciences. They must be treated in an adequate way before some multivariate analysis can be applied. Our procedure results from a modification of the Expectation-Maximization (EM) algorithm and is based on the additive log-ratio transformation. Its coherence with the nature of compositional data and with basic operations in the simplex sample space is checked. Using real data sets, we find that this approach improves other parametric and non-parametric techniques for compositional rounded zeros.