title: Pandas concatenation results in NaNs?
body: <p>What seems to be a simple function returns NaNs instead of the actual numbers. What am I missing here?</p>
  <pre><code>#Concatenate the dataframes:
  dfcal = dfcal.astype(float)
  dfmag = dfmag.astype(float)
  print('dfcal\n-----',dfcal)
  print('dfmag\n-----',dfmag)
  df = pd.concat([dfcal,dfmag])
  print('concatresult\n-----',df)
  </code></pre>
  <p><a href="https://i.stack.imgur.com/VGRiI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VGRiI.png" alt="enter image description here" /></a></p>
  <p>Cheers!</p>