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Backport PR #31943 on branch v3.11.x (FIX: allow non-strict monotonicity in LinearSegmented.from_list values) #31944

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Merged
QuLogic merged 1 commit into from
Jun 24, 2026
+8 −1
Merged

Backport PR #31943 on branch v3.11.x (FIX: allow non-strict monotonicity in LinearSegmented.from_list values) #31944

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2 changes: 1 addition & 1 deletion lib/matplotlib/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1233,7 +1233,7 @@ def from_list(name, colors, N=256, gamma=1.0, *, bad=None, under=None, over=None
except Exception as e2:
raise e2 from e
vals = np.asarray(_vals)
if np.min(vals) < 0 or np.max(vals) > 1 or np.any(np.diff(vals) <= 0):
if np.min(vals) < 0 or np.max(vals) > 1 or np.any(np.diff(vals) < 0):
raise ValueError(
"the values passed in the (value, color) pairs "
"must increase monotonically from 0 to 1."
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7 changes: 7 additions & 0 deletions lib/matplotlib/tests/test_colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1828,6 +1828,13 @@ def test_LinearSegmentedColormap_from_list_value_color_tuple():
)


def test_LinearSegmentedColormap_from_list_repeat_values():
# Smoke test that we can pass repeated values to make a solid band of color
# followed by a linear ramp.
value_color_tuples = [(0, "red"), (0.6, "red"), (0.6, "blue"), (1, "green")]
mcolors.LinearSegmentedColormap.from_list("lsc", value_color_tuples, N=11)


@image_comparison(['test_norm_abc.png'], remove_text=True, style='_classic_test',
tol=0 if platform.machine() == 'x86_64' else 0.05)
def test_norm_abc():
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