def precision_at_k()

in next_steps/data_science/offline_performance_evaluation/metrics.py [0:0]

• 6 lines of code
• 3 McCabe index (conditional complexity)

def precision_at_k(r, k):
    """Score is precision @ k

    Relevance is binary (nonzero is relevant).

    >>> r = [0, 0, 1]
    >>> precision_at_k(r, 1)
    0.0
    >>> precision_at_k(r, 2)
    0.0
    >>> precision_at_k(r, 3)
    0.33333333333333331
    >>> precision_at_k(r, 4)
    Traceback (most recent call last):
        File "<stdin>", line 1, in ?
    ValueError: Relevance score length < k


    Args:
        r: Relevance scores (list or numpy) in rank order
            (first element is the first item)

    Returns:
        Precision @ k

    Raises:
        ValueError: len(r) must be >= k
    """
    assert k >= 1
    r = [x!=0 for x in r[:k]]
    if np.size(r) != k:
        raise ValueError('Relevance score length < k')
    return np.mean(r)