Question

当x轴为datetime时，误差线图并不总是起作用：

z = pd.DataFrame({'timestamp': {0: pd.Timestamp('2018-06-16 04:33:27'),
  1: pd.Timestamp('2018-06-16 18:07:40')},
 'average': {0: 1.4158309812874796, 1: 1.4293226152856995},
 'stdev': {0: 0.5721450460404708, 1: 0.5771658975429514}})

现在z是

            timestamp   average     stdev
0 2018-06-16 04:33:27  1.415831  0.572145
1 2018-06-16 18:07:40  1.429323  0.577166

plt.plot(z.timestamp, z.average)可以正常工作，但plt.errorbar(z.timestamp, z.average, yerr=z.stdev)产生

<ErrorbarContainer object of 3 artists>
Error in callback <function install_repl_displayhook.<locals>.post_execute at 0x7fe251344840> (for post_execute):


Truncated Traceback (Use C-c C-x to view full TB):
~/.virtualenvs/algorisk/local/lib64/python3.6/site-packages/matplotlib/dates.py in viewlim_to_dt(self)
   1024                              'often happens if you pass a non-datetime '
   1025                              'value to an axis that has datetime units'
-> 1026                              .format(vmin))
   1027         return num2date(vmin, self.tz), num2date(vmax, self.tz)
   1028 

ValueError: view limit minimum -7.64586229992263e+16 is less than 1 and is an invalid Matplotlib date value. This often happens if you pass a non-datetime value to an axis that has datetime units

我在做什么错了？

PS。其他值似乎起作用。例如，

plt.errorbar(np.array([datetime.datetime(2018,7,30,12),
            datetime.datetime(2018,7,30,15)]).astype("datetime64[h]"),
         np.array([2,3]),
         yerr=np.array([1,2]))

按预期工作。

Answer 1

本机地，matplotlib可以绘制numpy数组。与其向绘图功能提供大熊猫Series，您可能不希望提供通过.values获得的底层numpy数组。

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame({'timestamp': {0: pd.Timestamp('2018-06-16 04:33:27'),
                                1: pd.Timestamp('2018-06-16 18:07:40')},
                  'average': {0: 1.4158309812874796, 1: 1.4293226152856995},
                  'stdev': {0: 0.5721450460404708, 1: 0.5771658975429514}})

plt.errorbar(df.timestamp.values, df.average.values, yerr=df.stdev.values)

plt.show()

针对日期时间的错误栏图失败

1 个答案: