| 摘要 |
A method of classifying an item of currency using a currency tester comprises sensing variable characteristics of a currency item and deriving a data vector (X) using values of the sensed characteristics, and transforming the data vector so that the variables represented by at least first and second sets of components (Y 1 , Y 2 ) of the transformed vector are substantially independent, so that the mahalanobis distance of X is substantially equivalent to the sum of the mahalanobis distances of the components (Y 1 , Y 2 ), and calculating a mahalanobis distance in at least two parts using said first and second sets of components.
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