[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: residue() confusion
From: |
Ben Abbott |
Subject: |
Re: residue() confusion |
Date: |
Sat, 22 Sep 2007 20:23:36 -0700 (PDT) |
I posted to one of the Fink forums and got this response
http://www.nabble.com/Trouble-with-Octave-tf4502632.html#a12842513
Apparently, the problem is with 2.9.13 and earlier. Can someone confirm?
Ben Abbott wrote:
>
> ok ... sigh ... I just noticed that
> http://www.nabble.com/bug-in-residue.m-tf4475396.html Hodel's original
> post has the same answer as I derived and is consistent with Matlab.
>
> So no my question is ...
>
> Does anyone's Octave installation give the wrong answer?
>
> Specifically is there someone with a Mac who used Fink to install Octave,
> and what does their installation give for
>
> num = [1 0 1];
> den = [1 0 18 0 81];
> [a,p,k,e] = residue(num,den)
>
>
>
> Ben Abbott wrote:
>>
>> ok, I did some quick math
>>
>> (x^2+1)/(x^4+18*x^2+81) = (2/9)/(x-3i) + (2/9)/(x+3i) + (1/54i)/(x-3i)^2
>> - (1/54i)/(x+3i)^2
>>
>> Thus,
>>
>> a = [1/54i 2/9 -1/54i 2/9]
>> p = [3i 3i -3i -3i]
>> k = []
>> e = [2 1 2 1]
>>
>> Can someone confirm they are able to get the correct answer from their
>> installation of Octave?
>>
>> I'm running 2.9.13 on both PPC and Intel based Macs
>>
>>
>> Ben Abbott wrote:
>>>
>>> Regarding the various results, I was more concerned about the
>>> differences in "a" ... the pole locations are consistent but their
>>> residues are different.
>>>
>>>
>>> Henry F. Mollet wrote:
>>>>
>>>> The result for e should be [1 2 1 2] (multiplicity for both poles).
>>>> Note
>>>> that Matlab does not even give e. My mis-understanding of the problem
>>>> was
>>>> pointed out by Doug Stewart. Doug posted new code yesterday, which I've
>>>> tried unsuccessfully, but I cannot be sure that I've implemented
>>>> residual.m
>>>> correctly. The corrected code still produced e = [1 1 1 1] for me.
>>>> Henry
>>>>
>>>>
>>>> on 9/22/07 1:31 PM, Ben Abbott at address@hidden wrote:
>>>>
>>>>>
>>>>> As a result of reading through Hodel's
>>>>> http://www.nabble.com/bug-in-residue.m-tf4475396.html post I decided
>>>>> to
>>>>> check to see how my Octave installation and my Matlab installation
>>>>> responded
>>>>> to the example
>>>>>
>>>>> Using Matlab v7.3
>>>>> --------------------------
>>>>> num = [1 0 1];
>>>>> den = [1 0 18 0 81];
>>>>> [a,p,k] = residue(num,den)
>>>>>
>>>>> a =
>>>>>
>>>>> 0 - 0.0926i
>>>>> 0.2222 - 0.0000i
>>>>> 0 + 0.0926i
>>>>> 0.2222 + 0.0000i
>>>>>
>>>>>
>>>>> p =
>>>>>
>>>>> 0.0000 + 3.0000i
>>>>> 0.0000 + 3.0000i
>>>>> 0.0000 - 3.0000i
>>>>> 0.0000 - 3.0000i
>>>>>
>>>>>
>>>>> k =
>>>>>
>>>>> []
>>>>> --------------------------
>>>>>
>>>>> Using Octave 2.9.13 (via Fink) on Mac OSX
>>>>> --------------------------
>>>>> num = [1 0 1];
>>>>> den = [1 0 18 0 81];
>>>>> [a,p,k] = residue(num,den)
>>>>>
>>>>> a =
>>>>>
>>>>> -3.0108e+06 - 1.9734e+06i
>>>>> -3.0108e+06 + 1.9734e+06i
>>>>> 3.0108e+06 + 1.9734e+06i
>>>>> 3.0108e+06 - 1.9734e+06i
>>>>>
>>>>> p =
>>>>>
>>>>> -0.0000 + 3.0000i
>>>>> -0.0000 - 3.0000i
>>>>> 0.0000 + 3.0000i
>>>>> 0.0000 - 3.0000i
>>>>>
>>>>> k = [](0x0)
>>>>> e =
>>>>>
>>>>> 1
>>>>> 1
>>>>> 1
>>>>> 1
>>>>> --------------------------
>>>>>
>>>>> These are different from both the result that
>>>>> http://www.nabble.com/bug-in-residue.m-tf4475396.html Hodel obtained ,
>>>>> as
>>>>> well as different from
>>>>> http://www.nabble.com/bug-in-residue.m-tf4475396.html Mollet's
>>>>>
>>>>> Thoughts anyone?
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Help-octave mailing list
>>>> address@hidden
>>>> https://www.cae.wisc.edu/mailman/listinfo/help-octave
>>>>
>>>>
>>>
>>>
>>
>>
>
>
--
View this message in context:
http://www.nabble.com/residue%28%29-confusion-tf4502015.html#a12842514
Sent from the Octave - General mailing list archive at Nabble.com.