[flexcoders] Charting - setting yField property for a PlotSeries when dataProvider is XML

[wreedijk]

I am trying to create a PlotChart with series (y is constant) from an
XML object that is defined as follows:

<series yVal='Weight'>
  <dataPoint date='12/01/2004'/> 
  <dataPoint date='12/25/2004'/>
  <dataPoint date='1/1/2005'/>
  <dataPoint date='1/22/2005'/>
</series>

I want the xField to be derived from the date attribute in the
dataPoint - no problem. I want the yField to be based on the yVal
attribute in the series (parent of the dataPoints) element. How can I
do this?

<mx:PlotSeries 
  dataProvider="{weightSeries.dataPoint}" 
  xField="@date" 
  yField=   ?? What do I put here ?? 
/>
There must be a way. Please help! Thanks

THE FOLLOWING WORKS but I don't want to have to repeat the y value in
every data point.

<series>
  <dataPoint date='12/01/2004' yVal='Weight'/> 
  <dataPoint date='12/25/2004' yVal='Weight'/>
  <dataPoint date='1/1/2005' yVal='Weight'/>
  <dataPoint date='1/22/2005' yVal='Weight'/>
</series>

<mx:PlotSeries 
  dataProvider="{weightSeries.dataPoint}" 
  xField="@date" 
  yField="@yVal"
/>