Multiclass-jaccard: fix off-by-one issue when ignore_index = num_clas…

…ses + 1 (#1860) fix off-by-one issue when ignore_index = num_classes + 1
Lightning-AI · Jun 28, 2023 · 8fef294 · 8fef294
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -221,6 +221,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed number of bugs related to `average="macro"` in classification metrics ([#1821](https://github.com/Lightning-AI/torchmetrics/pull/1821))
 
 
+- Fixed off-by-one issue when `ignore_index = num_classes + 1` in Multiclass-jaccard ([#1860](https://github.com/Lightning-AI/torchmetrics/pull/1860))
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 ## [0.11.4] - 2023-03-10
 
 ### Fixed

diff --git a/src/torchmetrics/functional/classification/jaccard.py b/src/torchmetrics/functional/classification/jaccard.py
@@ -65,7 +65,7 @@ def _jaccard_index_reduce(
     if average == "binary":
         return confmat[1, 1] / (confmat[0, 1] + confmat[1, 0] + confmat[1, 1])
 
-    ignore_index_cond = ignore_index is not None and 0 <= ignore_index <= confmat.shape[0]
+    ignore_index_cond = ignore_index is not None and 0 <= ignore_index < confmat.shape[0]
     multilabel = confmat.ndim == 3
     if multilabel:
         num = confmat[:, 1, 1]

diff --git a/tests/unittests/classification/test_jaccard.py b/tests/unittests/classification/test_jaccard.py
@@ -131,7 +131,7 @@ def _sklearn_jaccard_index_multiclass(preds, target, ignore_index=None, average=
     preds = preds.flatten()
     target = target.flatten()
     target, preds = remove_ignore_index(target, preds, ignore_index)
-    if ignore_index is not None and 0 <= ignore_index <= NUM_CLASSES:
+    if ignore_index is not None and 0 <= ignore_index < NUM_CLASSES:
         labels = [i for i in range(NUM_CLASSES) if i != ignore_index]
         res = sk_jaccard_index(y_true=target, y_pred=preds, average=average, labels=labels)
         return np.insert(res, ignore_index, 0.0) if average is None else res