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Better error message in scatter plot when len(x) != len(c) #7314
Description
import numpy as np
import matplotlib.pyplot as plt
N = 500
x = np.random.rand(N)
y = np.random.rand(N)
colors = np.random.rand(N+1)
fig, ax = plt.subplots()
ax.scatter(x, y, c=colors)
plt.show()raises the following error:
ValueError: Invalid RGBA argument: 0.23991184171163127
which is absolutely unrelated to the problem. We need a better error message when the color is not of the correct shape.
Activity
anntzer commented on Oct 21, 2016
The relevant lines are in the definition of scatter:
# After this block, c_array will be None unless # c is an array for mapping. The potential ambiguity # with a sequence of 3 or 4 numbers is resolved in # favor of mapping, not rgb or rgba. if c_none or co is not None: c_array = None else: try: c_array = np.asanyarray(c, dtype=float) if c_array.size == x.size: # <<- here is the interesting line. c = np.ma.ravel(c_array) else: # Wrong size; it must not be intended for mapping. c_array = None except ValueError: # Failed to make a floating-point array; c must be color specs. c_array = None if c_array is None: colors = c # must be acceptable as PathCollection facecolors else: colors = None # use cmap, norm after collection is createdIn fact the call to ravel leads to some more funny issues, e.g. the following code "works" when it likely shouldn't:
QuLogic commented on Nov 16, 2016
Fixed by #7363, I believe.