title: Resampling Dataframe Time series where column equals value
body: <p>I have been going through the documentation and trying different things but cant seem to find a solution for this.</p>
  
  <p>I have a df which contains multiple time series. Each time series object consist of a time, price, type of ec2 machine, and location. My goal is to be able to compare the same machine types in different locations and all the machine types within the same location.</p>
  
  <p><a href="https://i.stack.imgur.com/rAg36m.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rAg36m.png" alt="enter image description here"></a></p>
  
  <p>I need to resample these time series because the data is only collected when the price is changed, and so in order to do my desired analysis on them I need to resample to line up the times by the hour. I have this following code that will for example, resample one object, which is a specific machine type within a specific region. But how do I resample so that it resamples every Instance in a specific zone separately?</p>
  
  <pre><code>df.resample('H')
  df.fillna("ffill")
  df.head(10)
  </code></pre>