title: Pandas resample drops column
body: <p>Pandas is dropping one of my columns when resampling, and I don't understand why. I've read that this can happen if the columns don't have a proper numerical type, but that isn't the case here:</p>
  
  <pre><code>import pandas;
  
  # movements is the target data frame with daily movements
  movements = pandas.DataFrame(columns=['date', 'amount', 'cash']);
  movements.set_index('date', inplace=True);
  
  # df is a movement to add
  df = pandas.DataFrame({'amount': 179,
                         'cash':   100.00},
                         index=[pandas.Timestamp('2015/12/31')]);
  print(df); print(df.info()); print();
  
  # add df to movements and resample movements
  movements = movements.append(df).resample('D').sum().fillna(0);
  print(movements); print(movements.info());
  </code></pre>
  
  <p>results in:</p>
  
  <pre><code>            amount   cash
  2015-12-31     179  100.0
  &lt;class 'pandas.core.frame.DataFrame'&gt;
  DatetimeIndex: 1 entries, 2015-12-31 to 2015-12-31
  Data columns (total 2 columns):
  amount    1 non-null int64
  cash      1 non-null float64
  dtypes: float64(1), int64(1)
  memory usage: 24.0 bytes
  None
  
               cash
  2015-12-31  100.0
  &lt;class 'pandas.core.frame.DataFrame'&gt;
  DatetimeIndex: 1 entries, 2015-12-31 to 2015-12-31
  Freq: D
  Data columns (total 1 columns):
  cash    1 non-null float64
  dtypes: float64(1)
  memory usage: 16.0 bytes
  None
  </code></pre>
  
  <p>I noticed that the drop happens only when <code>cash</code> is a float, i.e. if in the code above <code>cash</code> is set to <code>100</code> (int) rather than <code>100.00</code>, then all columns are int and <code>amount</code> isn't dropped.</p>
  
  <p>Any idea?</p>