 Usage:  (y)=pansort(z,N)  
 
 Input:

  z Dataset              NT x {2+} k Matrix 
                         
  N Number of cross-section units (optional)  scalar 
                         
 Output:

  y Dataset ordered by cross-section units and  NT x {2+} k Matrix 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
