 Usage:  hrot = lpregrot(x {,p})  
 
 Input:

  x                      n x 2 vector, the data. 
                         
  p                      odd integer <=7, order of polynomial. If not 
                         given, p=1 (local linear) is used. 
                         
 Output:

  hrot                   scalar, rule-of-thumb bandwidth. 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
