CostEstimate_Structure:

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   Initialize a cost estimate data structure.

   Since version 7.
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   Form:
   cE = CostEstimate_Structure( nU );
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   Inputs
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   nU            (1)    Number of cost estimate structures = # of unique states

   -------
   Outputs
   -------
   cE            (.)    Cost estimate data structure with fields:
                          - nU
                          - memID
                          - targetIndex
                          - costLength
                          - cost

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