Fri Apr 19 21:15:47 EDT 2013

Transfer function computation

According to Porat, matrix inversion is not necessary.  However, for
my app, the transfer functions is not always SISO.  Still it might be
more efficient to compute all polynomials and memoize them, to
accelerate computation multiple evaluation of the transfer function,
instead of performing a matrix inversion per different frequency

EDIT: To spit out C code for transfer function computation, it might
be best to use this approach..  Otoh, for 2D systems, the matrix
inversion isn't going to be problematic.