1. A method of generating a spectral feature vector, said method comprising the steps of: accepting at least two input vectors, each input vector including spectral features; creating vectors of ranks via ranking values of the spectral features of each input vector; creating ordered vectors via arranging the values of each input vector according to rank; creating a vector of ordered average values via determining the average of corresponding values of the ordered vectors; creating a vector of ordered average ranks via determining the sum or average of the vectors of ranks; creating a vector of ordered ranks via ranking the values of the ordered average ranks; creating a spectral feature vector via employing the rank order represented by the vector of ordered ranks to reorder the vector of ordered average ranks.