Re: problem with consistency of root finding and sorting

[David Bateman]

Ben Abbott wrote:
>
> Thanks David,
>
> another attempt, if you don't mind
>
> p = roots([1 0 18 0 81])
> p =
>
>   -0.0000 + 3.0000i
>   -0.0000 - 3.0000i
>    0.0000 + 3.0000i
>    0.0000 - 3.0000i
>
octave:1> p = roots([1 0 18 0 81])
p =

   0.0000 + 3.0000i
   0.0000 - 3.0000i
  -0.0000 + 3.0000i
  -0.0000 - 3.0000i

> [e, indx] = mpoles (p)
> e =
>
>    1
>    2
>    1
>    2
>
> indx =
>
>    1
>    3
>    2
>    4

octave:2> [e, indx] = mpoles (p)
e =

   1
   2
   1
   2

indx =

   2
   4
   1
   3

>
> p(indx)
> ans =
>
>   -0.0000 + 3.0000i
>    0.0000 + 3.0000i
>   -0.0000 - 3.0000i
>    0.0000 - 3.0000i
>
>
>
octave:3> p(indx)
ans =

   0.0000 - 3.0000i
  -0.0000 - 3.0000i
   0.0000 + 3.0000i
  -0.0000 + 3.0000i


-- 
David Bateman                                address@hidden
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