Table 1 The multi-functions of genes defy a straightforward estimation of the mutual information. Each gene is assigned to a vector of binary attributes A = {A₁, A₂, ..., $A_{N_A}$}, described by a number a _i ∈ [0, $2^{N_A}$ - 1]. The contingency table to evaluate the mutual information I(C, [A₁, ..., $A_{N_A}$]), taking all possible combinations into account, would thus include up to $2^{N_A}$ columns.

From: Validation and functional annotation of expression-based clusters based on gene ontology