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   Create an object of class quat. You can input:
   4-by-1 matrix - assumed to be a quaternion
   3-by-1 matrix - assumed to be an array of angles
   3-by-3 matrix - assumed to be a transformation matrix
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   Form:
   q = quat( x )
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   Inputs
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   x       (3,1) Quaternion
           (3,3) Matrix
           (3,1) Array of angles

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   Outputs 
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   q      (1,1) Object of class  quaternion.

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