FIX Avoid setting legend when labels are None in RocCurveDisplay kwargs #29727
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sklearn/metrics/_plot/roc_curve.py
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| if "label" in line_kwargs or "label" in chance_level_line_kw: | ||
| if ( | ||
| line_kwargs.get("label") is not None | ||
| and chance_level_line_kw.get("label") is not None |
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Isn't it an or and instead of an and? We need one of the two not being None to show the legend?
It also means that we don't have a test right now.
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Yes, I did change the logic so that the legend is not set as soon as either of the labels is None.
The reasoning is that I don't think anyone would set plot_chance_lvl=True and override chance_level_kw with {"label": None}, so that part could be a bit more flexible. WDYT?
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For me this is counter-intuitive to have no legend for the chance level curve with the following code:
In [3]: import matplotlib.pyplot as plt
...: from sklearn.datasets import make_classification
...: from sklearn.metrics import RocCurveDisplay
...: from sklearn.model_selection import train_test_split
...: from sklearn.svm import SVC
...: X, y = make_classification(random_state=0)
...: X_train, X_test, y_train, y_test = train_test_split(
...: X, y, random_state=0)
...: clf = SVC(random_state=0).fit(X_train, y_train)
...: RocCurveDisplay.from_estimator(
...: clf, X_test, y_test, label=None, plot_chance_level=True
...: )
...: plt.show()If I really want to turn off the legend for the chance level then I can do it with the right params:
In [2]: import matplotlib.pyplot as plt
...: from sklearn.datasets import make_classification
...: from sklearn.metrics import RocCurveDisplay
...: from sklearn.model_selection import train_test_split
...: from sklearn.svm import SVC
...: X, y = make_classification(random_state=0)
...: X_train, X_test, y_train, y_test = train_test_split(
...: X, y, random_state=0)
...: clf = SVC(random_state=0).fit(X_train, y_train)
...: RocCurveDisplay.from_estimator(
...: clf, X_test, y_test, label=None, plot_chance_level=True, chance_level_kw={"label": None},
...: )
...: plt.show()So to have this last behaviour you need to have a or operator and not a and operator.
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We will need an additional test to check that the behaviour is the one that we want. |
| @@ -193,7 +198,6 @@ def test_roc_curve_chance_level_line( | |||
| assert display.chance_level_.get_linestyle() == "--" | |||
| assert display.chance_level_.get_label() == "Chance level (AUC = 0.5)" | |||
| elif plot_chance_level: | |||
| assert display.chance_level_.get_label() == chance_level_kw["label"] | |||
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I removed this test as it is redundant with the assert chance_level_kw["label"] in legend_labels added further below.
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I addressed all your comments @glemaitre. Also I don't really think we need a changelog entry here, unless you think otherwise. |
Reference Issues/PRs
What does this implement/fix? Explain your changes.
In #29617 and #29611 the RocCurveDisplay is used to visualize the roc curve across several cross-validation splits. As having the labels for each split is unnecessary, we rather set
label=None, but that rises aUserWarning: No artists with labels found to put in legenddue to the legend being set at a lower level inside the display.This PR fixes the issue.
Any other comments?
Notice that
"label" in chance_level_line_kwand"label" in line_kwargsare always True, as those keys are assigned earlier in the code. As "label" cannot be removed, only updated toNone, we rather query for it's value using thegetmethod.