Re: problem with residue and repeated complex roots

[Doug Stewart]

Thanks
Doug

Ben Abbott wrote:
> Doug,
>
> This problem was addressed with a change that made it into 2.9.16. If 
> you check the cvs you can replace your residue.m with the one there. 
> You'll need mpoles.m as well.
>
> I should also mention that another bug/feature was fixed just yesterday.
>
> Ben
>
> On Nov 27, 2007, at 5:11 PM, Doug Stewart wrote:
>
> > I am running qtoctave on windows XP octave version 2.9.15
> > residue doesn't give the correct answer for repeated complex roots
> >
> > her is Matlab's result
> >
> > » n
> > n =
> >      1
> > » d
> > d =
> >      1     8    42   104   169
> > » roots(d)
> > ans =
> >   -2.0000+ 3.0000i
> >   -2.0000- 3.0000i
> >   -2.0000+ 3.0000i
> >   -2.0000- 3.0000i
> > » [a b c]=residue(n,d)
> > a =
> >   1.0e+005 *
> >    1.2662+ 1.8232i
> >    1.2662- 1.8232i
> >   -1.2662- 1.8232i
> >   -1.2662+ 1.8232i
> > b =
> >   -2.0000+ 3.0000i
> >   -2.0000- 3.0000i
> >   -2.0000+ 3.0000i
> >   -2.0000- 3.0000i
> > c =
> >      []
> >
> > and qtoctave's results
> >
> > > > n
> >
> > n = 1
> >
> > > > d
> >
> > d =
> >
> > 1 8 42 104 169
> >
> > > > roots(d)
> >
> > ans =
> >
> > -2.0000 + 3.0000i
> >
> > -2.0000 - 3.0000i
> >
> > -2.0000 + 3.0000i
> >
> > -2.0000 - 3.0000i
> >
> > > > [a b c]=residue(n,d)
> >
> > a =
> >
> > -9.3613e-018 - 9.2593e-003i
> >
> > -2.7778e-002 - 5.3894e-010i
> >
> > 2.3130e-018 + 9.2593e-003i
> >
> > -2.7778e-002 + 5.3894e-010i
> >
> > b =
> >
> > -2.0000 + 3.0000i
> >
> > -2.0000 + 3.0000i
> >
> > -2.0000 - 3.0000i
> >
> > -2.0000 - 3.0000i
> >
> > c = [](0x0)
> >
> >
> >
> > I haven't looked into why this is happening yet.
> >
> > Doug Stewart
> >
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