In the original data set, 15 volatile compounds (descriptors of coffee aroma) were selected for a statistical analysis. We selected six compounds (compositional parts) on three sorts of coffee.
References
M. Korhonov\'a, K. Hron, D. Klimc\'ikov\'a, L. Muller, P. Bedn\'ar, and P. Bart\'ak (2009). Coffee aroma - statistical analysis of compositional data. Talanta, 80(2): 710--715.