“…In order to overcome the nonlinearity problem, several methods such as principal curves [8], locally linear PCA methods [9], the nonlinear iterative PLS algorithm for PLS [10,11] and kernel PCA [12][13][14] have been introduced and applied in practice [15][16][17]. In order to overcome the nonlinearity problem, several methods such as principal curves [8], locally linear PCA methods [9], the nonlinear iterative PLS algorithm for PLS [10,11] and kernel PCA [12][13][14] have been introduced and applied in practice [15][16][17].…”