title: Pandas subplots plotting multiple y-axis
body: <p>I have a dataframe that looks like this. I need a subplot for each unique Item (book, Table and Chair). The plots should be sorted by Year (Year is also the x-axis).  I need to make use of twiny to have Price on the left and Quantity plotted on the right of each subplot. </p>
  
  <p>I can do this manually for each Item by creating a individual dataframe. So I created a dataframe for Book, then sorted by Year and set Year as index. then create the plot with secondary_y.  But obviously this is long winded. Is there a way to do this from the original dataframe without all the manual processing?  </p>
  
  <pre><code>    Item  Year Price  Quantity
  0   Book  2000    $2        50
  1  Table  2000   $33        44
  2  Chair  2000   $21        31
  3   Book  2001    $3        77
  4  Table  2001   $20       500
  5  Chair  2001    $2        50
  6   Book  2002   $36         7
  7  Table  2002  $200        50
  8  Chair  2002   $44         5
  </code></pre>