Ranking
Some notes on ranking techniques
Basics
Pointwise, Pairwise and Listwise Learning to Rank
Point-wise ranking
In point-wise ranking, you have some scores for you document
Metrics
Cumulative Gain
Suppose you have a list of results
Then the cumulative gain at position
The discounted cumulative gain (DCG) takes the position into account, discounting lower-ranked results:
The normalized discounted cumulative gain (NDCG) is 1-normalized by dividing over the best possible ranking: