3. A system according to claim 1 , wherein the clusters are generated based on a similarity metric comprising forming a score vector for each uncoded electronically stored information item in the portion and each coded electronically stored information item in the reference set and calculating the similarity metric by comparing the score vectors for one of the uncoded electronically stored information items and one of the coded electronically stored information items in the reference set as an inner product.
4. A system according to claim 3 , wherein the inner product is determined according to the following equation: cos ⁢ ⁢ σ AB = 〈 S → A · S → B 〉  S → A  ⁢  S → B  where cos σ AB comprises a similarity between uncoded electronically stored information item A and coded reference electronically stored information item B, {right arrow over (S)} A comprises a score vector for the uncoded electronically stored information item A, and {right arrow over (S)} B comprises a score vector for the coded reference electronically stored information item B.