Fig 2. Chemical space of the training and test sets as described by the principal component analysis (PCA).

The first two components, and their representation in % of the total variance are shown. (A). PCA of the training set’ inhibitors of PubChem vs. ChEMBL data sets. (B) PCA of the external test set’ inhibitors of PubChem vs. ChEMBL data sets. (C) PCA of the training and external test sets’ inhibitors. (D) PCA of the training and external test sets’ non-inhibitors.