<rrd_graph_def>
  <options>
    <vertical_label>Millibars</vertical_label>
  </options>
  <datasources>
    <def>
      <name>barometer</name>
      <rrd>${rrdFile}</rrd>
      <source>barometer</source>
      <cf>AVERAGE</cf>
    </def>
    <cdef>
      <name>barometerMb</name>
      <rpn>barometer,33.86,*</rpn>
    </cdef>
  </datasources>
  <graph>
    <line>
      <datasource>barometerMb</datasource>
      <color>#FF0000</color>
      <legend>Barometric pressure</legend>
    </line>
  </graph>
</rrd_graph_def>