 Usage:  xyaug = spfill(x,y, a, b, h, r)  
 
 Input:

  x                      n x 1 matrix 
                         
  y                      n x 1 matrix 
                         
  a                      scalar, lower limit for estimation 
                         
  b                      scalar, upper limit for estimation 
                         
  h                      scalar, bandwidth 
                         
  r                      scalar, scaling factor 
                         
 Output:

  xyaug                  n x 2 matrix, is the augmented and sorted data 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
