Fix the calculation of the optimal predictions

youden_index.py

@@ -107,11 +107,11 @@ class YoudenIndex(evaluate.Metric):
         # 1. Compute ROC AUC
         roc_auc = roc_auc_score(references, prediction_scores)
         # 2. Determine the optimal threshold based on the Youden index
-        fpr, tpr, thresholds = roc_curve(references, prediction_scores)
+        fpr, tpr, thresholds = roc_curve(references, prediction_scores, drop_intermediate=False)
         idx = np.argmax(tpr - fpr)
-        optimal_threshold = thresholds[idx-1]
+        optimal_threshold = thresholds[idx]
         # 3. Calculate PPV (precision) and NPV based on the optimal threshold
-        optimal_predictions = np.where(prediction_scores > optimal_threshold, 1, 0)
+        optimal_predictions = np.where(prediction_scores >= optimal_threshold, 1, 0)
         ppv = precision_score(references, optimal_predictions)
         npv = precision_score(references, optimal_predictions, pos_label=0)
         return {