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Discounted cumulative gain (DCG) is a measure of ranking quality. In information retrieval, it is often used to measure effectiveness of web search engine algorithms or related applications. Using a graded relevance scale of documents in a search engine result set, DCG measures the usefulness, or ''gain'', of a document based on its position in the result list. The gain is accumulated from the top of the result list to the bottom with the gain of each result discounted at lower ranks.〔Kalervo Jarvelin, Jaana Kekalainen: Cumulated gain-based evaluation of IR techniques. ACM Transactions on Information Systems 20(4), 422–446 (2002)〕 == Overview == Two assumptions are made in using DCG and its related measures. # Highly relevant documents are more useful when appearing earlier in a search engine result list (have higher ranks) # Highly relevant documents are more useful than marginally relevant documents, which are in turn more useful than irrelevant documents. DCG originates from an earlier, more primitive, measure called Cumulative Gain. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Discounted cumulative gain」の詳細全文を読む スポンサード リンク
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