Abstract: A device comprises first frequency calculating means (142) for calculating a function value IDF(P) of the frequency of an index word in a document (d) to be examined in a group of documents (P) to be compared, second frequency calculating means (171) for calculating a function value IDF(S) of the frequency of the index word in a group of similar documents (S) similar to the document (d), coordinate transforming means (181) for transforming the position of each index word by conformal mapping on a coordinate system where the calculated function value IDF (P) goes on a first axis of the coordinate system and the calculated function value IDF(S) goes on a second axis, and output means (4) for outputting the index words and their positioning data according to the transformed coordinate data of the index words. With this, the character of the document is accurately expressed, or the tendency of the whole of the documents group to be examined can be analyzed.

Abstract: A device comprises input means (1) for inputting a document (d) to be examined, a group of documents (P) to be compared, and a group of similar documents (S), index word extracting means (120) for extracting an index word in the document (d), first frequency calculating means (143) for calculating in GFIDF(P) of the extracted index word in the document group (P), second frequency calculating means (171) for calculating in GFIDF(S) of the extracted index word in the similar document group (S), and output means (4) for outputting the index words and their positioning data according to the combination of the calculated ln GFIDF(P) and ln GFIDF(S) in the document group to be compared and the similar document group. With this, when a document to be examined is given, the assertion of the document can be easily grasped.

Abstract: A document correlation diagram drawing device includes extracting means (20, 30) for extracting content data and time data of document elements (E) each including one or more documents, dendrogram drawing means (50) for drawing a dendrogram showing a correlation between documents on the basis of the content data of the document elements, clustering means (70) for cutting the dendrogram in accordance with a predetermined rule and extracting clusters, and intra-cluster arranging means (90) for determining an intra-cluster arrangement of the document elements belonging to each cluster on the basis of the time data of the document elements. Accordingly, a dendrogram adequately showing the chronological development in each field can be automatically drawn.

Abstract: An index term extraction device including: input means (1) for inputting a document-to-be-surveyed d and documents-to-be-compared P; index term extraction means (120) for extracting an index term from the document-to-be-surveyed d; first appearance frequency calculation means (142) for calculating a function value IDF (P) of the appearance frequency of the extracted index term in the documents-to-be-compared P; similar documents selecting means (160) for selecting similar documents S similar to the document-to-be-surveyed d in the documents-to-be-compared P according to the data on the document-to-be-surveyed d; second appearance frequency calculation means (171) for calculating the function value IDF (S) of the appearance frequency of the extracted index term in the similar documents S; and output means (4) for outputting each index term and its positioning data according to the combination of the function values of the respective appearance frequencies in the documents-to-be-compared and the similar documen

Abstract: A keyword extracting device includes high-frequency term extracting means (30) for extracting high-frequency terms which are index terms having a great weight among the index terms in a document group (E) including a plurality of documents (D), the weight including evaluation on the level of an appearance frequency of each index term, clustering means (50) for clustering the high-frequency terms on the basis of a co-occurrence degree C. which is based on the presence/absence of the co-occurrence of each document with the index terms (w) in the document group (E) in each document, score calculating means (70) for calculating a score key(w) of each index term (w) such that a high score is given to the index term among the index terms (w) that co-occurs with the high-frequency term belonging to more clusters (g) and that co-occurs with the high-frequency term in more documents (D), and keyword extracting means (90) for extracting keywords on the basis of the scores.