[Octave-bug-tracker] [bug #49291] residue function gives incompatible result

[Rik]

Follow-up Comment #3, bug #49291 (project octave):

More thoughts, since residue is invertible it should be able to apply residue
twice and arrive back at the original inputs.  This works for more ordinary
inputs, but not for the special case presented here.  I made a script,
tst_res.m, which is attached.


rf = [1e3 2e3 1e3 2e3];
cf = [316.2e-9 50e-9 31.6e-9 5e-9];
r = 1./cf
p = -1./(rf.*cf)
k = 0
[b, a] = residue (r, p, k);
[r2, p2, k2] = residue (b, a)


When running it in Octave I get,


tst_res
r =

   3.1626e+06   2.0000e+07   3.1646e+07   2.0000e+08

p =

  -3.1626e+03  -1.0000e+04  -3.1646e+04  -1.0000e+05

k = 0
r2 =

   3.1703e+06
   2.3710e+07
   2.1554e+07

p2 =

  -3.1573e+03
  -1.1024e+04
  -1.9857e+04

k2 =  1759.6


As you can see, r2 and p2 don't even have the correct number of elements, and
k2 is wildly off from 0.


(file #38683)
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Additional Item Attachment:

File name: tst_res.m                      Size:0 KB


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