Defining the similarity between two communities and identifying the number of clusters. (a) We define the similarity between two communities c and c' as the sum of pairwise similarities between the members of c and the members of c'. (b) This figure shows the largest eigenvalues of a sample from the stem cell dataset. The number of clusters is estimated according to the knee point of eigenvalues curve. This point is defined as the intersection of the above regression line and the line y = 1. The horizontal coordinate of the knee point estimates the number of spectral clusters.
Zare et al. BMC Bioinformatics 2010 11:403 doi:10.1186/1471-2105-11-403