Figure 3: Synthesized data including 500 samples and the contours of the first three principal components drawn using a polynomial kernel. The first row is from KPCA, the second row is from TP-IKPCA, the third row is from IKPCA-RS, and the forth row is from INKPCA. Data points are represented by red dots “” and the green lines are the contour lines of constant value of the first three principal components.