 Usage:  y = replace(x,w,b)  
 
 Input:

  x                      array, string or numeric. 
                         
  w                      scalar or vector, the value to be replaced. 
                         
  b                      scalar, the value to replace. 
                         
 Output:

  y                      array, numeric, matrix x after all 
                         values w are replaced by b. 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
