RowCompU:

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   Computes the upper row compression of a matrix. Compresses the 
   matrix a so that

   comp(a) = [ r ]
             [ 0 ]

   r is of full row rank, i.e. the rows are linearly independent.
   Zero rows are determined by the singular values.

   Since version 1.
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   Form: 
   [r, uh, ac] = RowCompU( a, neps )
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   ------
   Inputs
   ------
   a                   Matrix
   neps                Multiple of machine epsilon to be used
                       as the tolerance for a zero row

   -------
   Outputs
   -------
   r                   Upper row compression of a
   uh                  ac = uh*a
   ac                  a compressed

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   References: Maciejowski, J.M., Multivariable Feedback Design, Addison-
               Wesley, 1989, pp. 366.
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