Distribution of the gn-lnX score (see Table 1) for samples where both genes are frequent and samples where both genes are infrequent, for each sample class. Dashed lines correspond to positive samples (gene pairs where the products of the two genes belong to the same metabolic or signaling pathway or protein complex), solid lines correspond to negative samples (all other pairs). Note that the curves are distributions, not histograms. Hence, the large unbalance between positive and negative samples cannot be seen here. (Left) Distributions before normalization. (Right) Distributions after znorm composed normalization.