Figure 4.

Transformation of the serum network into the plasma network (or vice versa) by varying the thresholds imposed on the weighted adjacency matrices. The Frobenius norm is used to assess differences between the connectivity matrices. The Frobenius norm is always larger than 0; therefore, it can be concluded that it is not possible to transform one network into the other: The metabolites association networks obtained from samples in studies Ia and Ib (NMR, 29 metabolites, plasma and serum from different blood samples) are inherently different in plasma and serum. (CLR denotes Context Likelihood of Relatedness, ARACNE is Algorithm for the Reconstruction of Accurate Cellular Networks, PCLRC is Probabilistic Context Likelihood of Relatedness on Correlations, and CORR is Pearson's correlation.)