Metrics dcg

Dcg

The unnormalized half of the pair. It answers "how much relevance is near the top?" in the units the relevance was given in, so it grows with those values and has no upper bound — two rows are comparable only when their relevance judgements are on the same scale.

That is the reason it is rarely the number reported, and the reason it is here anyway: Ndcg is this divided by its own ideal, and a surprising NDCG is usually explained by looking at the two halves separately.

Alone among the four types on this page it takes a logBase, because dcg_score does — the discount does not cancel here, so changing its base changes the answer.

Members

Member	What it does
Dcg.Score	The mean discounted gain over the rows.