title: How to get the actual vAxis max value of Google Chart API?
body: <p>I have two Line Charts and each has a <code>rangeFilter</code> (like the one <a href="https://code.google.com/apis/ajax/playground/?type=visualization#chartrangefilter_control" rel="nofollow noreferrer">here</a>.)</p>
  
  <p>I want to synchronize the scale of the two charts. That is, when one chart changes the range view, it will change <code>vAxis max value</code> to suit the maximum data in that range, and I want the other chart to change the scale to the same value.</p>
  
  <p>How can I get the <code>vAxis.viewWindow.max</code> in <em>realtime</em>?</p>