 Usage:  y = grbiplot(x,r,k)  
 
 Input:

  x                      n x p matrix (n >= p) (n cases, p variables) 
                         
  r                      number, rank of approximation (d <= p) 
                         
  k                      number, 0 <= k <= 1 
                         
 Output:

  b                      n+p x d matrix, containing the coordinates for the 
                         biplot 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
