Example of Laplacian eigenvectors. Here are four example of Laplacian eigenvectors of the main component of KEGG. The colours correspond to the coefficients of the eigenvectors: positive coefficients are marked in red, negative coefficients are in green, and the intensity of the colour reflects the absolute values of the coefficients. On the upper-left side is the eigenvector associated with the smallest eigenvalue, on the upper-right side the one associated with the second smallest eigenvalues, on the lower-left side, the one associated with the third smallest eigenvalue while on the lower-right side is the one associated with the largest eigenvalue. The larger the eigenvalue, the less smooth the corresponding eigenvector.