Figure 2.

(A) Overview of the statistical procedure used to establish the association $r{c}_{\mathrm{A}}(x_i,x_j)$ (eqn (6)) between the metabolite and lipids pairwise correlations $C(x_i,x_j)$ (eqn (3)), with the group age (Figure 1). In the case of ratios (eqn (7)), the correlation matrix is replaced with the matrix of pairwise ratios, for average abundances is replaced by the vectors of means (eqn (8)). (B). Overview of the data-splitting procedure used to validate the results. Each subject group is randomly split into 2 halves, obtaining 2 sets of 20 groups. The analysis is performed on the first set, while the second set is used for validation. The procedure is repeated 100 times: Only results validated more than 50% of the times are considered significant.