 Usage:  d = discrim(x1, x2, x)  
 
 Input:

  x1                     n1 x p matrix (sample 1) 
                         
  x2                     n2 x p matrix (sample 2) 
                         
  x                      p x 1 vector (the obs to be classified) 
                         
 Output:

  d                      1 x 2 vector (the distance to the two samples) 
                         Note 
                         It is assumed that both samples have identical cov structure 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
