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   Plot simulation data.

   To load data from the workspace:

     PlottingTool( 'load sim data', d );

   where "d" is a data structure with fields:
           .time
           .data
           .dataNames
           .scNames
           .units
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   Form:
   tag = PlottingTool( action, modifier )
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   ------
   Inputs
   ------
   action          (1,:)   Action to be taken 
   modifier        (:)     Modifier to the message

   -------
   Outputs
   -------
   tag             (1,:)   Returns the window tag on initialization

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