eval_nDCG | R Documentation |
Metric for information retrival where positions are discounted logarithmically.
eval_nDCG(recommendedIDX, testSetIDX)
recommendedIDX |
indices of the recommended items. Object of class |
testSetIDX |
indices of the items in the test set. Object of class |
nDCG is computed as the ratio between Discounted Cumulative Gain(DCG) and idealized Discounted Cumulative Gain(IDCG):
DGC_{pos} = rel_1 + ∑_{i=2}^{pos} \frac{rel_i}{\log_2i}
IDGC_{pos} = rel_1 + ∑_{i=2}^{|h|-1} \frac{rel_i}{\log_2i}
nDCG_{pos} = \frac{DCG}{IDCG}
Asela Gunawardana, Guy Shani, Evaluating Recommender Systems.
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