Bug report

Matplotlib.pyplot eventplot function is raising an error when i try to generate a raster plot. Given a sequence of event timings, and an equally sized sequence of lineoffsets, the error message 'ValueError: lineoffsets and positions are unequal sized sequences' is returned. Changing the dtype to np.array for both variables does not help.

Reproducible with:

import matplotlib.pyplot as plt

events=[197, 2175, 4153] # event timings for a single subject
lineoffsets = [1, 1, 1]
plt.eventplot(events, lineoffsets=lineoffsets)

Actual outcome
Traceback (most recent call last):
File "", line 1, in
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/pyplot.py", line 2567, in eventplot
else {}), **kwargs)
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/init.py", line 1589, in inner
return func(ax, *map(sanitize_sequence, args), **kwargs)
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/axes/_axes.py", line 1376, in eventplot
raise ValueError('lineoffsets and positions are unequal sized '
ValueError: lineoffsets and positions are unequal sized sequences

lineoffsets = [1,3]
plt.eventplot(events, lineoffsets=lineoffsets)
Traceback (most recent call last):
File "", line 1, in
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/pyplot.py", line 2567, in eventplot
else {}), **kwargs)
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/init.py", line 1589, in inner
return func(ax, *map(sanitize_sequence, args), **kwargs)
File "/home/nd17878/anaconda3/lib/python3.7/site-packages/matplotlib/axes/_axes.py", line 1376, in eventplot
raise ValueError('lineoffsets and positions are unequal sized '
ValueError: lineoffsets and positions are unequal sized sequences