 Usage:  hrot = lpderrot(x {,q {,p}} {,K})  
 
 Input:

  x                      n x 2 vector, the data. 
                         
  q                      integer <=4, order of derivative. If not 
                         given, q=1 (first derivative) is used. 
                         
  p                      integer, order of polynomial. Must be q+1 
                         or q+3. If not given, p=q+1 is used. 
                         
 Output:

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