title: Count the number of metrics in Graphite that are currently between two values
body: <p>Help me with this otherwise very simple task... I have a series of metrics that represent a certain virtual machine state. I want to plot a graph with the count of all metrics that have been between a certain range (35-51). This is my query:</p>
  
  <pre><code>countSeries(filterSeries(filterSeries(opennebula-performance.zones.opennebula-innologica.vms.3DC.*.vm_lcm_state, 'min' , '&gt;', 35 ), 'max', '&lt;', 51))
  </code></pre>
  
  <p>This seems to be working well when there is at least one metric in the range. However when there are none (and it's the common case since there aren't usually faulty VMs), Graphite returns just <code>[]</code> instead of series with zeroes. Grafana doesn't like this and plots <code>no data</code>. </p>
  
  <p>Why doesn't <code>countSeries</code> return 0 when there are no matches? This will indeed plot a straight line at <code>0</code> for the whole period, but this is exactly what is needed here.</p>
  
  <p>My Graphite version is <code>1.2.0-dev</code>, but on previous versions this didn't work too.</p>