model_eval.py 文件源码

def compute_pr(y_test, probability_predictions):
    """
    Compute Precision-Recall, thresholds and PR AUC.

    Args:
        y_test (list) : true label values corresponding to the predictions. Also length n.
        probability_predictions (list) : predictions coming from an ML algorithm of length n.

    Returns:
        dict: 

    """
    _validate_predictions_and_labels_are_equal_length(probability_predictions, y_test)

    # Calculate PR
    precisions, recalls, pr_thresholds = skmetrics.precision_recall_curve(y_test, probability_predictions)
    pr_auc = skmetrics.average_precision_score(y_test, probability_predictions)

    # get ideal cutoffs for suggestions (upper right or 1,1)
    pr_distances = (precisions - 1) ** 2 + (recalls - 1) ** 2

    # To prevent the case where there are two points with the same minimum distance, return only the first
    # np.where returns a tuple (we want the first element in the first array)
    pr_index = np.where(pr_distances == np.min(pr_distances))[0][0]
    best_precision = precisions[pr_index]
    best_recall = recalls[pr_index]
    ideal_pr_cutoff = pr_thresholds[pr_index]

    return {'pr_auc': pr_auc,
            'best_pr_cutoff': ideal_pr_cutoff,
            'best_precision': best_precision,
            'best_recall': best_recall,
            'precisions': precisions,
            'recalls': recalls,
            'pr_thresholds': pr_thresholds}