Z2S:

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   Transform an z-plane transfer function into the s-plane.

   If only 3 inputs are given it assumes the input is in transfer
   function form. Otherwise it assumes state equation form.

   Since version 1.
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   Form:
   [a, b, c, d] = Z2S( f, g, h, j, dT, sType )       
   [nums, dens] = Z2SBl( numz, denz, dT, sType )
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   ------
   Inputs
   ------
   f                  Discrete state matrix or numerator polynomial
   g                  Discrete input matrix or denominator polynomial
   h                  Output matrix
   j                  Feedthrough matrix
   T                  Sampling period
   sType              'bilinear', 'zoh', 'forward', 'backward'

   -------
   Outputs
   -------
   a                  State matrix or nums
   b                  Input matrix or dens
   c                  Output matrix or T
   d                  Feedthrough matrix

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	References:	Franklin, G.F., J.D. Powell, M.L. Workman, Digital Control
               of Dynamic Systems, 2nd Edition, Addison-Wesley, 1990, p. 137.
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Children:

Common: Control/ND2SS
Common: Control/SS2ND
Math: Linear/DelLZ