Patent ID: 7451139

Claim:
A clustering apparatus comprising: a memory; a Central Processing Unit: a similarity calculation unit which respectively calculates a similarity as a relative value between documents, with respect to combinations of a plurality of documents, using a document vector and a significance of a word included in a document; a conversion unit which converts similarity calculated by the similarity calculation unit to an absolute value by normalization; and a clustering unit which executes clustering of a plurality of documents, based on similarity of the absolute value; wherein the absolute value is a sum of a ratio between a similarity having a highest value and a similarity to be converted and a ratio between a mean value of similarities and the similarity to be converted, or the absolute value is a ratio between the similarity having the highest value among the similarities not be converted and the similarity to be converted, said normalization being carried out in accordance with a following equation: normalized similarity=α×(similarity of target document/similarity of document of first place)+β×(similarity of target document/mean value of the similarities), wherein α and β are coefficients, and wherein α is 0 and β is 1, and a number of higher ranking documents is 1, the above equation can be expressed as following equation: Normalized similarity=(similarity of target document/highest similarity in documents other than relevant document), and wherein a result of said normalization identifying at least one of said plurality of documents relative to the relevant document is output.