MahalanobisDistance:

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   Compute the Mahalanobis Distance.

   In statistics, Mahalanobis distance is a distance measure based on
   correlations between variables.

   This appears in the exponential term of the multivariate Gaussian.

   Type MahalanobisDistance for a demo.

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   Form:
   d = MahalanobisDistance( x, mu, s )
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   Inputs
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   x           (:,1)   State
   mu          (:,1)   Mean
   s           (:,:)   Covariance matrix

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   Outputs
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   d           (1,1)   Mahalanobis Distance

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   Reference: http://en.wikipedia.org/wiki/Mahalanobis_distance
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