Handle case of empty preds or gt

src/batdetect2/evaluate/match.py

@@ -139,19 +139,31 @@ def greedy_match(
     Tuple[Optional[int], Optional[int], float]
         A 3-element tuple describing a match or a miss. There are three
         possible formats:
-        - Successful Match: `(target_idx, source_idx, affinity)`
-        - Unmatched Source (False Positive): `(None, source_idx, 0)`
-        - Unmatched Target (False Negative): `(target_idx, None, 0)`
+        - Successful Match: `(source_idx, target_idx, affinity)`
+        - Unmatched Source (False Positive): `(source_idx, None, 0)`
+        - Unmatched Target (False Negative): `(None, target_idx, 0)`
     """
     assigned = set()
 
+    if not source:
+        for target_idx in range(len(target)):
+            yield None, target_idx, 0
+
+        return
+
+    if not target:
+        for source_idx in range(len(source)):
+            yield source_idx, None, 0
+
+        return
+
     if scores is None:
         indices = np.arange(len(source))
     else:
         indices = np.argsort(scores)[::-1]
 
-    for index in indices:
-        source_geometry = source[index]
+    for source_idx in indices:
+        source_geometry = source[source_idx]
 
         affinities = np.array(
             [
@@ -169,19 +181,19 @@ def greedy_match(
         affinity = affinities[closest_target]
 
         if affinities[closest_target] <= affinity_threshold:
-            yield index, None, 0
+            yield source_idx, None, 0
             continue
 
         if closest_target in assigned:
-            yield index, None, 0
+            yield source_idx, None, 0
             continue
 
         assigned.add(closest_target)
-        yield index, closest_target, affinity
+        yield source_idx, closest_target, affinity
 
     missed_ground_truth = set(range(len(target))) - assigned
-    for index in missed_ground_truth:
-        yield None, index, 0
+    for target_idx in missed_ground_truth:
+        yield None, target_idx, 0
 
 
 def match_sound_events_and_raw_predictions(