索引（x 轴）作为 datetime64[ns] 不起作用答案

【问题标题】：Index (x axis) as datetime64[ns] not working索引（x 轴）作为 datetime64[ns] 不起作用
【发布时间】：2021-04-29 14:42:52
【问题描述】：

我有一个看起来像这样的数据框：

           Open time     Open     High      Low    Close        4_EMA       20_EMA  Position
0 2021-03-30 12:00:00  1848.86  1849.04  1826.05  1830.61  1830.610000  1830.610000       NaN
1 2021-03-30 16:00:00  1830.61  1858.29  1827.78  1858.27  1841.674000  1833.244286       1.0
2 2021-03-30 20:00:00  1858.27  1859.13  1833.50  1840.46  1841.188400  1833.931497       0.0
3 2021-03-31 00:00:00  1840.41  1862.55  1810.99  1823.17  1833.981040  1832.906592       0.0
4 2021-03-31 04:00:00  1823.18  1855.55  1801.00  1813.89  1825.944624  1831.095488      -1.0
...

Complete csv here.

我的情节代码是：

import pandas as pd
import matplotlib.pyplot as plt

df4 = pd.read_csv('data/df_4h.csv', parse_dates=['Open time']) 

#df4.set_index('Open time', inplace=True) # this line causes the problem

fig, (ax2) = plt.subplots(1, 1, figsize=(15, 10))

df4['Close'].plot(ax=ax2, color = 'k', lw = 1, label = 'Close Price')
df4['4_EMA'].plot(ax=ax2, color = 'b', lw = 1, label = '4_EMA')
df4['20_EMA'].plot(ax=ax2, color = 'g', lw = 1, label = '20_EMA')
        
# plot 'buy' signals
ax2.plot(df4[df4['Position'] == 1].index, 
        df4['4_EMA'][df4['Position'] == 1], 
        '^', markersize = 15, color = 'g', alpha = 0.7, label = 'buy')

# plot 'sell' signals
ax2.plot(df4[df4['Position'] == -1].index, 
        df4['4_EMA'][df4['Position'] == -1], 
        'v', markersize = 15, color = 'r', alpha = 0.7, label = 'sell')


plt.show()

这样效果很好：

Image plot 1

问题是当我尝试将 set_index 作为 Open time 列时，箭头不再显示，我不明白为什么，我需要在 x 轴刻度上插入此列，所以如果我：

...
df4.set_index('Open time', inplace=True)
...

生成的情节没有箭头（买卖，df4['4_EMA'][df4['Position'] == 1] 或 df4['4_EMA'][df4['Position'] == -1]）：

Image plot 2

如何保留箭头并在 x 轴上显示日期时间？

【问题讨论】：

标签： python python-3.x pandas matplotlib

【解决方案1】：

问题在于您将绘图与pandas（与df.plot）和matplotlib（与ax2.plot）结合使用。 pandas 选项使用转换后的索引进行绘图。

您可以将两者都更改为使用pandas，例如：

df4 = pd.read_csv('https://pastebin.pl/view/raw/1046cfca',
                  parse_dates=['Open time']) 

df4.set_index('Open time', inplace=True)

fig, (ax2) = plt.subplots(1, 1, figsize=(15, 10))

df4['Close'].plot(ax=ax2, color = 'k', lw = 1, label = 'Close Price')
df4['4_EMA'].plot(ax=ax2, color = 'b', lw = 1, label = '4_EMA')
df4['20_EMA'].plot(ax=ax2, color = 'g', lw = 1, label = '20_EMA')
        
ax2.set_title("4H time frame")

# ----------------------------------------------------------------------
# the following is changed to use `df.plot`:
# ----------------------------------------------------------------------

# plot 'buy' signals
df4.loc[df4['Position']==1, '4_EMA'].plot(
    ls='None', marker='^', markersize = 15,
    color = 'g', alpha = 0.7, label = 'buy', ax=ax2)

# plot 'sell' signals
df4.loc[df4['Position']==-1, '4_EMA'].plot(
    ls='None', marker='v', markersize = 15,
    color = 'r', alpha = 0.7, label = 'sell', ax=ax2)

plt.show()

输出：

【讨论】：