相关疑难解决方法(0)

升级 matplotlib 后，我失去了针对日期时间对象进行绘图的能力。

错误如下：

  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/pyplot.py", line 2813, in plot
    is not None else {}), **kwargs)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/__init__.py", line 1810, in inner
    return func(ax, *args, **kwargs)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 1611, in plot
    for line in self._get_lines(*args, **kwargs):
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 393, in _grab_next_args
    yield from self._plot_args(this, kwargs)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 370, in _plot_args
    x, y = self._xy_from_xy(x, y)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 204, in _xy_from_xy
    bx = self.axes.xaxis.update_units(x)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axis.py", line 1475, in update_units
    self.set_units(default)
  File "/opt/anaconda3/envs/py36/lib/python3.6/site-packages/matplotlib/axis.py", line 1548, in set_units …

下图

import matplotlib
f= plt.figure(figsize=(12,4))
ax = f.add_subplot(111)
df.set_index('timestamp')['values'].plot(ax=ax)
ax.xaxis.set_major_locator(matplotlib.dates.HourLocator(interval=1))
ax.xaxis.set_major_formatter(matplotlib.dates.DateFormatter('%I'))
plt.show()

即使我有以下情况，也会在错误的区域（GMT）中显示小时：

> df['timestamp'][0]
Timestamp('2014-09-02 18:37:00-0400', tz='US/Eastern')

实际上，如果我注释掉这一行：

ax.xaxis.set_major_formatter(matplotlib.dates.DateFormatter('%I'))

在正确的时区中显示小时。

为什么？