Fix plotting of metric collection when prefix/postfix is set (#2429)

* implementation
* add tests
* changelog

(cherry picked from commit 0a82679)

CHANGELOG.md

@@ -33,6 +33,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed dtype being changed by deepspeed for certain regression metrics ([#2379](https://github.com/Lightning-AI/torchmetrics/pull/2379))
 
 
+- Fixed plotting of metric collection when prefix/postfix is set ([#2429](https://github.com/Lightning-AI/torchmetrics/pull/2429))
+
+
 - Fixed bug when `top_k>1` and `average="macro"` for classification metrics ([#2423](https://github.com/Lightning-AI/torchmetrics/pull/2423))
 
 

src/torchmetrics/collections.py

@@ -647,12 +647,11 @@ def plot(
                     f"Expected argument `ax` to be a sequence of matplotlib axis objects with the same length as the "
                     f"number of metrics in the collection, but got {type(ax)} with len {len(ax)} when `together=False`"
                 )
-
         val = val or self.compute()
         if together:
             return plot_single_or_multi_val(val, ax=ax)
         fig_axs = []
-        for i, (k, m) in enumerate(self.items(keep_base=True, copy_state=False)):
+        for i, (k, m) in enumerate(self.items(keep_base=False, copy_state=False)):
             if isinstance(val, dict):
                 f, a = m.plot(val[k], ax=ax[i] if ax is not None else ax)
             elif isinstance(val, Sequence):

tests/unittests/utilities/test_plot.py

@@ -855,12 +855,17 @@ def test_confusion_matrix_plotter(metric_class, preds, target, labels, use_label
 
 @pytest.mark.parametrize("together", [True, False])
 @pytest.mark.parametrize("num_vals", [1, 2])
-def test_plot_method_collection(together, num_vals):
+@pytest.mark.parametrize(
+    ("prefix", "postfix"), [(None, None), ("prefix", None), (None, "postfix"), ("prefix", "postfix")]
+)
+def test_plot_method_collection(together, num_vals, prefix, postfix):
     """Test the plot method of metric collection."""
     m_collection = MetricCollection(
         BinaryAccuracy(),
         BinaryPrecision(),
         BinaryRecall(),
+        prefix=prefix,
+        postfix=postfix,
     )
     if num_vals == 1:
         m_collection.update(torch.randint(0, 2, size=(10,)), torch.randint(0, 2, size=(10,)))