Fig. 2: Dimension reduction techniques applied to the Paroni Sterbini dataset.

The plots represent the best dimension reduction results based on PSI-PR projection-based separability index (PSI) for the three different labels (P-treated, untreated H+ and untreated H−), evaluated in the 2D embedding space. Moreover, also the average values of all pairwise PSI-ROC are reported as overall estimators of separation between the groups in the 2D reduced space. a PCA; b MDS with Bray-Curtis dissimilarity (MDSbc); c MDS with weighted UniFrac distance (MDSwUF); d nonmetric MDS with Sammon Mapping (NMDS); e MCE. Blue dots represent PPI-treated samples, while red and green dots are the untreated samples which resulted either negative (red) or positive (green) to the H. pylori test (histological observation and urease test). f The curves in three different colours (red, blue and green) highlight the different distributions of the three groups on the second dimension for the MCE plot (e).