matchzoo.metrics.normalized_discounted_cumulative_gain

Normalized discounted cumulative gain metric for ranking.

Module Contents

class matchzoo.metrics.normalized_discounted_cumulative_gain.NormalizedDiscountedCumulativeGain(k:int=1, threshold:float=0.0)

Bases: matchzoo.engine.base_metric.RankingMetric

Normalized discounted cumulative gain metric.

ALIAS = ['normalized_discounted_cumulative_gain', 'ndcg']

__repr__(self)

Returns:Formated string representation of the metric.

__call__(self, y_true:np.array, y_pred:np.array)

Calculate normalized discounted cumulative gain (ndcg).

Relevance is positive real values or binary values.

Example

>>> y_true = [0, 1, 2, 0]
>>> y_pred = [0.4, 0.2, 0.5, 0.7]
>>> ndcg = NormalizedDiscountedCumulativeGain
>>> ndcg(k=1)(y_true, y_pred)
0.0
>>> round(ndcg(k=2)(y_true, y_pred), 2)
0.52
>>> round(ndcg(k=3)(y_true, y_pred), 2)
0.52
>>> type(ndcg()(y_true, y_pred))
<class 'float'>

Parameters:

• y_true – The ground true label of each document.
• y_pred – The predicted scores of each document.

Returns:

Normalized discounted cumulative gain.