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Re: problem with consistency of root finding and sorting
From: |
David Bateman |
Subject: |
Re: problem with consistency of root finding and sorting |
Date: |
Wed, 10 Oct 2007 13:55:26 +0200 |
User-agent: |
Thunderbird 1.5.0.7 (X11/20060921) |
Ben Abbott wrote:
>
> On Oct 10, 2007, at 3:45 AM, David Bateman wrote:
>
>> 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
>>
>
> Thanks again. I believe I've found the bug ... and it is mine :-(
>
> Using the attached mpoles.m, I get
>
> 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
>
> I assume you will get the same.
>
>
>
Ok with the attached mpoles at the latest CVS I get
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
octave:2> [e, indx] = mpoles(p)
e =
1
2
1
2
indx =
3
1
4
2
octave:3> p(indx)
ans =
-0.0000 + 3.0000i
0.0000 + 3.0000i
-0.0000 - 3.0000i
0.0000 - 3.0000i
D.
--
David Bateman address@hidden
Motorola Labs - Paris +33 1 69 35 48 04 (Ph)
Parc Les Algorithmes, Commune de St Aubin +33 6 72 01 06 33 (Mob)
91193 Gif-Sur-Yvette FRANCE +33 1 69 35 77 01 (Fax)
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- problem with consistency of root finding and sorting, Ben Abbott, 2007/10/09
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/09
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/09
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/09
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/09
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting,
David Bateman <=
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10