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Description
Bug report
Trying to plot XY positions and associated (world-space) angles using quiver.
I would like the arrows to have a fixed length in axis-space but, what I think is the correct combination of options, does not correctly calculate the length variable in Quiver._make_verts.
Code for reproduction
import matplotlib.pyplot as plt
import numpy as np
x = np.arange(10)
y = np.zeros_like(x)
u = np.ones_like(x)
v = np.ones_like(x)
angles = np.random.rand(*x.shape)
angles *= 360.0
angles -= 180.0
_, axis = plt.subplots()
axis.quiver(x, y, u, v, angles=angles, scale=1.0, scale_units="xy")
plt.show()Actual outcome
Traceback (most recent call last):
File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1540, in __call__
return self.func(*args)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/backends/backend_tkagg.py", line 280, in resize
self.show()
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/backends/backend_tkagg.py", line 351, in draw
FigureCanvasAgg.draw(self)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 464, in draw
self.figure.draw(self.renderer)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/figure.py", line 1143, in draw
renderer, self, dsu, self.suppressComposite)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
a.draw(renderer)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 2409, in draw
mimage._draw_list_compositing_images(renderer, self, dsu)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
a.draw(renderer)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/artist.py", line 63, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/quiver.py", line 533, in draw
verts = self._make_verts(self.U, self.V)
File "/home/j/jk/jk421/.local/lib/python2.7/site-packages/matplotlib/quiver.py", line 628, in _make_verts
a = lengths
UnboundLocalError: local variable 'lengths' referenced before assignment
Expected outcome
10 arrows with a fixed length in axis-space and random angles.
Matplotlib version
- Operating system: Ubuntu 16.04 (LTS) x86_64
- Matplotlib version: 2.0.0
- Matplotlib backend (
print(matplotlib.get_backend())): TkAgg - Python version: 2.7.12
- Jupyter version (if applicable):
- Other libraries:
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