title: how to draw graph? (x=datetime, y=price)
body: <p>I type some code to show the relationship between price and datetime about bitcoin.So I want to draw the graph to show them BUT it fail, i dont know the reason, please give me some tips,thanks a lot.</p>
  <p><strong>below is my code</strong></p>
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  
  import pandas as pd
  df = pd.read_csv(r'D:\downloads\BTC-USD.csv', date_parser = True)
  
  
  df.columns = ['datetime','open','high','low','close','adj', 'vol']
  
  print(df.head(5))
  
  df.index = df['datetime']
  
  
  
  
  df.datetime=pd.to_numeric(df.datetime,errors='coerce')
  df.adj=pd.to_numeric(df.adj,errors='coerce')
  
  print(df[['datetime', 'adj']].plot(kind = 'line', figsize=[20,5]))
  </code></pre>
  <p><strong>below is the terminal result</strong></p>
  <pre><code>PS D:\python&gt; python test3.py
  0  2020-10-30  13437.874023  ...  13546.522461  30581485201
  1  2020-10-31  13546.532227  ...  13780.995117  30306464719
  2  2020-11-01  13780.995117  ...  13737.109375  24453857900
  3  2020-11-02  13737.032227  ...  13550.489258  30771455468
  4  2020-11-03  13550.451172  ...  13950.300781  29869951617
  
  [5 rows x 7 columns]
  PS D:\python&gt; python test3.py
       datetime          open  ...           adj          vol
  0  2020-10-30  13437.874023  ...  13546.522461  30581485201
  1  2020-10-31  13546.532227  ...  13780.995117  30306464719
  2  2020-11-01  13780.995117  ...  13737.109375  24453857900
  3  2020-11-02  13737.032227  ...  13550.489258  30771455468
  4  2020-11-03  13550.451172  ...  13950.300781  29869951617
  
  [5 rows x 7 columns]
  AxesSubplot(0.125,0.11;0.775x0.77)
  </code></pre>