title: Plotting two dataframe time-series on same graph with different sampling (and using double Y axis)
body: <p>I have two data frames that look like:</p>
  
  <pre><code>                  Temp [Degrees_C]  Cond [mS/cm]    
  yyyy-mm-ddThh:mm:ss.sss             
  2020-01-28 03:00:59 14.553947   19.301285   
  2020-01-28 08:00:59 14.501740   19.310037   
  2020-01-28 13:00:59 14.425415   18.531609   
  2020-01-28 18:00:59 14.414717   16.155998   
  ...
  </code></pre>
  
  <p>And this:</p>
  
  <pre><code>                    CONDUCTIVITY    Temp [C]
  DATE TIME           
  2020-01-28 03:00:00     18.240  15.761111
  2020-01-28 04:00:00     18.147  15.722222
  2020-01-28 05:00:00     17.930  15.722222
  2020-01-28 06:00:00     17.873  15.666667
  ...
  </code></pre>
  
  <p>I want to create one plot using these two data sets, they should share the same x-axis as the date-time, and two different y-axes (one for temperature and one for conductivity).
  However, since the sampling is different for both of them, I'm not sure how to do it.</p>
  
  <p>Any suggestions?</p>
  
  <p>Thank you!!</p>