precision_recall_curve.py

def plot_precision_vs_recall(precisions, recalls, metric_name=None, metric_perc=None):
    plt.figure(figsize=(15, 10))
    plt.plot(recalls, precisions, 'b-', linewidth=2)
    plt.xlabel("Recall", fontsize=15)
    plt.ylabel("Precision", fontsize=15)
    plt.axis([0, 1, 0, 1])
    if metric_name=='precision':
        # tradedoff recall  & threshold at percentage precision we want.
        recall_atperc_precision = recalls[np.argmax(precisions >= metric_perc)] 
        threshold_atperc_precision = thresholds[np.argmax(precisions >= metric_perc)]
        plt.plot([recall_atperc_precision, recall_atperc_precision], [0., metric_perc], 'r:')
        plt.plot([0., recall_atperc_precision], [metric_perc, metric_perc], "r:")
        plt.plot([recall_atperc_precision], [metric_perc], 'ro')
        plt.title("Precision/Recall plot with Threshold Set to {}% of {}\n trading off Recall at {:.3f}%".format(
            metric_perc*100, 
            metric_name.capitalize(), 
            tradedoff_atperc_metric*100), fontsize=20)
        plt.show()
        return threshold_atperc_precision
    elif metric_name == 'recall':
        # tradedoff precision & threshold at percentage recall we want.
        precision_atperc_recall = precisions[np.argmax(recalls <= metric_perc)] 
        threshold_atperc_recall = thresholds[np.argmax(recalls <= metric_perc)]
        plt.plot([0., metric_perc],[precision_atperc_recall, precision_atperc_recall], 'r:')
        plt.plot([metric_perc, metric_perc],[0., precision_atperc_recall], "r:")
        plt.plot([metric_perc],[precision_atperc_recall], 'ro')
        plt.title("Precision/Recall plot with Threshold Set to {}% of {}\n trading off Precision at {:.3f}%".format(
            metric_perc*100, 
            metric_name.capitalize(), 
            precision_atperc_recall*100), fontsize=20)
        plt.show()
        return threshold_atperc_recall
    else:
        return

threshold = plot_precision_vs_recall(precisions, recalls, 'recall', 0.9)