SizeAB:

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   Checks the dimensions of the set a, b for consistency.

   Since version 2.
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   Form:
   notOK = SizeAB( a, b )
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   ------
   Inputs
   ------
   a                   Plant matrix
   b                   Input matrix

   -------
   Outputs
   -------
   notOK               Not correct if equal to 0

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