title: How to join a Series to a DataFrame?
body: <p>Is there any way to join a Series to a DataFrame directly? </p>
  
  <p>The join would be on a field of the dataframe and on the index of the series. </p>
  
  <p>The only way I found was to convert the series to a dataframe first, as in the code below.</p>
  
  <pre><code>import numpy as np
  import pandas as pd
  
  df = pd.DataFrame()
  df['a'] = np.arange(0, 4)
  df['b'] = np.arange(100, 104)
  
  
  s = pd.Series(data=np.arange(100, 103))
  
  # this doesn't work
  # myjoin = pd.merge(df, s, how='left', left_on='a', right_index=True)
  
  # this does
  s = s.reset_index()
  # s becomes a Dataframe
  # note you cannot reset the index of a series inplace
  myjoin = pd.merge(df, s, how='left', left_on='a', right_on='index')
  
  print myjoin
  </code></pre>