Closed
Description
Bug summary
contour (and friends) specify that a single string can be passed to colors:
As a shortcut, single color strings may be used in place of one-element lists
But this only works when levels is the same length as the color string.
Code for reproduction
import numpy as np
import matplotlib.pyplot as plt
x = np.arange(1, 10)
y = x.reshape(-1, 1)
h = x * y
cs = plt.contour(h, levels=[10, 30, 50],
colors='green', extend='both')Actual outcome
colors='green' gives error (while colors='red' works, or making levels to be length of 5 also works):
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[64], line 8
5 y = x.reshape(-1, 1)
6 h = x * y
----> 8 cs = plt.contour(h, levels=[10, 30, 50],
9 colors='green', extend='both')
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/pyplot.py:3143, in contour(data, *args, **kwargs)
3141 @_copy_docstring_and_deprecators(Axes.contour)
3142 def contour(*args, data=None, **kwargs) -> QuadContourSet:
-> 3143 __ret = gca().contour(
3144 *args, **({"data": data} if data is not None else {}), **kwargs
3145 )
3146 if __ret._A is not None: # type: ignore[attr-defined]
3147 sci(__ret)
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/__init__.py:1473, in _preprocess_data.<locals>.inner(ax, data, *args, **kwargs)
1470 @functools.wraps(func)
1471 def inner(ax, *args, data=None, **kwargs):
1472 if data is None:
-> 1473 return func(
1474 ax,
1475 *map(sanitize_sequence, args),
1476 **{k: sanitize_sequence(v) for k, v in kwargs.items()})
1478 bound = new_sig.bind(ax, *args, **kwargs)
1479 auto_label = (bound.arguments.get(label_namer)
1480 or bound.kwargs.get(label_namer))
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/axes/_axes.py:6659, in Axes.contour(self, *args, **kwargs)
6650 """
6651 Plot contour lines.
6652
(...)
6656 %(contour_doc)s
6657 """
6658 kwargs['filled'] = False
-> 6659 contours = mcontour.QuadContourSet(self, *args, **kwargs)
6660 self._request_autoscale_view()
6661 return contours
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/contour.py:847, in ContourSet.__init__(self, ax, levels, filled, linewidths, linestyles, hatches, alpha, origin, extent, cmap, colors, norm, vmin, vmax, extend, antialiased, nchunk, locator, transform, negative_linestyles, clip_path, *args, **kwargs)
845 cmap.set_under(self.colors[0])
846 if self._extend_max:
--> 847 cmap.set_over(self.colors[-1])
849 # label lists must be initialized here
850 self.labelTexts = []
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/colors.py:834, in Colormap.set_over(self, color, alpha)
832 def set_over(self, color='k', alpha=None):
833 """Set the color for high out-of-range values."""
--> 834 self._rgba_over = to_rgba(color, alpha)
835 if self._isinit:
836 self._set_extremes()
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/colors.py:314, in to_rgba(c, alpha)
312 rgba = None
313 if rgba is None: # Suppress exception chaining of cache lookup failure.
--> 314 rgba = _to_rgba_no_colorcycle(c, alpha)
315 try:
316 _colors_full_map.cache[c, alpha] = rgba
File ~/miniconda3/envs/sklearn-env/lib/python3.12/site-packages/matplotlib/colors.py:391, in _to_rgba_no_colorcycle(c, alpha)
387 raise ValueError(
388 f"Invalid string grayscale value {orig_c!r}. "
389 f"Value must be within 0-1 range")
390 return c, c, c, alpha if alpha is not None else 1.
--> 391 raise ValueError(f"Invalid RGBA argument: {orig_c!r}")
392 # turn 2-D array into 1-D array
393 if isinstance(c, np.ndarray):
ValueError: Invalid RGBA argument: 'n'
Expected outcome
Does not depend on color string length.
Additional information
I think it is because we don't convert to list if colors is given as string, and then we do this:
matplotlib/lib/matplotlib/contour.py
Lines 835 to 836 in ef32d22
Operating system
Ubuntu
Matplotlib Version
3.9.2
Matplotlib Backend
No response
Python version
No response
Jupyter version
No response
Installation
None