Fig. 3.

(a) [Left] An illustration of an unsupervised learning using p-SNE with open image database Olivetti faces, where similar images (same person) are clustered automatically without providing any identity information. (b) [Right (reprint permission granted)] Dawson et al. [13] demonstrated that PCA can be used to observe clinical data structure. In this case the data describing the xerostomia occurrences due to parotid gland dose distributions is linearly separable.