title: Creating a matplotlib multi-series line plot with pandas
body: <p>I want to create a multi series line plot showing how the occurrences of a data-frame element change over time:</p>
  
  <p>I have two lists in which I have joined in a dataframe:</p>
  
  <pre><code>df = pd.DataFrame(
  {'Date': datelist,
   'Category': catlist
  })
  </code></pre>
  
  <p>I have then grouped the dataframe to show the counts of each occurrence over time:</p>
  
  <pre><code>df = df.groupby(['Date', 'Category']).size()
  print df
  </code></pre>
  
  <p>This returns something that looks like this:</p>
  
  <pre><code> Date        Category        
   13/02/2018  clean          2
               suspicious     1
   14/02/2018  clean          2
   19/02/2018  clean          2
  </code></pre>
  
  <p>I now want to create a multi-series line plot for each category type, showing how the count changes over date.</p>
  
  <p>I'm really not sure how to do this using matplotlib</p>