[Octave-bug-tracker] [bug #51148] residue function potentially inaccurate

[Marco Caliari]

Follow-up Comment #12, bug #51148 (project octave):

The problem is in the subfunction rresidue in residue.m. It is dangerous to
compute pn as deconvolution of pden and current pm (around line 340). In fact,
pm is the product of all the other denominators. If you replace 


pn = deconv (pden, pm);


with


pn = 1;
for j = indx(1):n - 1
  pn = conv (pn, [1, -p(j)]);
end
for j = n + 1:indx(end)
  pn = conv (pn, [1, -p(j)]);
end
for j = 1:e(n) - 1
  pn = deconv (pn, [1, -p(n)]);
end


you get the right solution. I'm still not satisfied with the last
deconvolution step. Any better idea?

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