Figure 1.

Illustrative example of the discretization process. This figure shows: (Left) Original expression matrix A'; and (Right) Discretized matrix A obtained by considering a simple discretization technique, which uses a three symbol alphabet Σ = {D, N, U}. The symbols mean down-regulation (D), up-regulation (U) or no-change (N). In this case, the values ∈ ]-0.3, 0.3[ were discretized to N, and the values ≤ -0.3 and ≥ 0.3 were discretized to D and U, respectively.