[metrics] Return an F1 of 0 in TableCellMetric when no cell matches

doctr/utils/metrics.py

@@ -380,11 +380,10 @@ def summary(self) -> dict[str, float | None]:
         """
         recall = self.matches / self.num_gts if self.num_gts > 0 else None
         precision = self.matches / self.num_preds if self.num_preds > 0 else None
-        f1 = (
-            2 * precision * recall / (precision + recall)
-            if precision is not None and recall is not None and (precision + recall) > 0
-            else None
-        )
+        f1 = None
+        if precision is not None and recall is not None:
+            # No match at all gives a precision and a recall of 0, so an F1 of 0
+            f1 = 2 * precision * recall / (precision + recall) if (precision + recall) > 0 else 0.0
         structure_acc = self.struct_matches / self.matches if self.matches > 0 else None
         return {"recall": recall, "precision": precision, "f1": f1, "structure_acc": structure_acc}
 

tests/common/test_utils_metrics.py

@@ -612,5 +612,12 @@ def test_table_cell_metric(use_polygons):
     res = metric.summary()
     assert res["recall"] == 0.0 and res["precision"] is None and res["structure_acc"] is None
 
+    # Cells on both sides but no match -> recall, precision and F1 are 0
+    metric = metrics.TableCellMetric(iou_thresh=0.5, use_polygons=use_polygons)
+    metric.update(gt_cells[:1], gt_logic[:1], gt_cells[2:], gt_logic[2:])
+    res = metric.summary()
+    assert res["recall"] == 0.0 and res["precision"] == 0.0 and res["f1"] == 0.0
+    assert res["structure_acc"] is None
+
     metric.reset()
     assert metric.num_gts == metric.num_preds == metric.matches == metric.struct_matches == 0