title: How to apply resample to a pandas Dataframe with not numerical value
body: <p>I learned that <code>resample</code> cannot be applied with not numerical value from
  <a href="https://stackoverflow.com/questions/34257069/resampling-pandas-dataframe-is-deleting-column">Resampling pandas dataframe is deleting column</a>
  and, I would like to apply <code>resample('30S')</code> to the input df as in the following:   </p>
  
  <p>Input_DF:</p>
  
  <pre><code>    eventTime          uuid  ts                   m_op  op.prg  op.tr     w.cycle cycle_type
  0  2017-04-27 01:22:22 id1  2017-04-27 02:30:30   w     0.0     01:34:48  3       type_a                                                       
  1  2017-04-27 01:23:16 id1  2017-04-27 02:31:00   w     1.0     01:33:54  3       type_a                                                      
  2  2017-04-27 01:25:10 id1  2017-04-27 02:41:00   w     2.0     01:33:00  3       type_a                                                      
  3  2017-04-27 01:25:32 id1  2017-04-27 02:42:45   w     3.0     01:32:00  3       type_a                                                     
  4  2017-04-27 01:25:45 id1  2017-04-27 02:52:45   r     4.0     01:32:00  2       type_a                                                     
  </code></pre>
  
  <p>Output_DF</p>
  
  <pre><code>    eventTime          uuid  ts                   m_op  op.prg  op.tr     w.cycle cycle_type
  0  2017-04-27 01:22:30 id1  2017-04-27 02:30:30   w     0.0     01:34:48  3       type_a                                                       
  1  2017-04-27 01:23:00 id1  2017-04-27 02:30:30   w     0.0     01:34:48  3       type_a                                                       
  2  2017-04-27 01:23:30 id1  2017-04-27 02:31:00   w     1.0     01:33:54  3       type_a                                                      
  3  2017-04-27 01:24:00 id1  2017-04-27 02:31:00   w     1.0     01:33:54  3       type_a                                                      
  4  2017-04-27 01:24:30 id1  2017-04-27 02:31:00   w     1.0     01:33:54  3       type_a                                                      
  5  2017-04-27 01:25:00 id1  2017-04-27 02:31:00   w     1.0     01:33:54  3       type_a                                                      
  6  2017-04-27 01:25:30 id1  2017-04-27 02:41:00   w     2.0     01:33:00  3       type_a                                                      
  7  2017-04-27 01:26:00 id1             avg    +popular  3.5     Avg      +popular       type_a                
  </code></pre>
  
  <p>where  <code>avg_of_the_values</code> compute the avg among the corresponding times, <code>+popular</code> fill with the most popular value or the first one -in case of two values with the same rank - and <code>Avg</code> is the usual mean.                                     </p>
  
  <p>I have been applying <code>groupBy</code> approach but it did not work.<br>
  Any suggestion would be very appreciated in advance. Many thanks in advance.carlo </p>