title: Plotting a multiple column in Pandas (converting strings to floats)
body: <p>I'd like to plot "MJD" vs "MULTIPLE_MJD" for the data given here::
  <a href="https://www.dropbox.com/s/cicgc1eiwrz93tg/DR14Q_pruned_several3cols.csv?dl=0" rel="nofollow noreferrer">https://www.dropbox.com/s/cicgc1eiwrz93tg/DR14Q_pruned_several3cols.csv?dl=0</a></p>
  
  <pre><code>import numpy as np
  import pandas as pd
  
  import matplotlib.pyplot as plt
  import ast
  
  filename = 'DR14Q_pruned_several3cols.csv'
  datafile= path+filename
  df = pd.read_csv(datafile)
  
  df.plot.scatter(x='MJD', y='N_SPEC')
  plt.show()
  
  ser = df['MJD_DUPLICATE'].apply(ast.literal_eval).str[1]
  df['MJD_DUPLICATE'] = pd.to_numeric(ser, errors='coerce')
  df['MJD_DUPLICATE_NEW'] = pd.to_numeric(ser, errors='coerce')
  
  df.plot.scatter(x='MJD', y='MJD_DUPLICATE')
  plt.show()
  </code></pre>
  
  <p>This makes a plot, but only for one value of MJD_DUPLICATE::</p>
  
  <pre><code>print(df['MJD_DUPLICATE_NEW'])
  </code></pre>
  
  <p>0       55214
     1       55209
     ...</p>
  
  <p>Thoughts??</p>