NDCG
Discounted cumulative gain (DCG) DCG measures the usefulness, or gain, of a document based on its position in the result list
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.
sum(rel[i] / log2(i) for i in range(p)) rel[i] - relevance of result i p - rank position p
alternative:
sum((2 ** rel[i] - 1) / log2(i + 1) for range(p))