  COMMAND PWAVE2D
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    Purpose: transversal/longitudinal particle-wave along x- and y-axis
      Usage: PWAVE2D(<particleID>,<frames>,<filename>,<"T" or "L">,<saveFormat>,
             [<amplitude>,<wavelength>,<sourceX>,<sourceY>,
             <damping>,<phase in degrees>])
   Examples: pwave2d(1,40,obj,l,obj,12.0,24,10,-10,1.6,60.0)
             pwave2d(1,60,,l,particle)
             pwave2d(1,60,ram:obj,t,obj)
