[Octave-bug-tracker] [bug #63393] Bode plot problem. Different results between MATLAB and Octave.

[Luiz Antonio Maccari Junior]

URL:
  <https://savannah.gnu.org/bugs/?63393>

                 Summary: Bode plot problem. Different results between MATLAB
and Octave.
                 Project: GNU Octave
               Submitter: luiz
               Submitted: seg 21 nov 2022 13:57:52
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: Luiz Antonio Maccari Jr.
        Originator Email: 
             Open/Closed: Open
                 Release: 7.2.0
         Discussion Lock: Any
        Operating System: Any


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Follow-up Comments:


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Date: seg 21 nov 2022 13:57:52       By: Luiz Antonio Maccari Junior <luiz>
Dear developers,

I have found a different behavior from MATLAB and Octave bode function. I am
taking the frequency response of a high-order discrete transfer function and
getting different results from MATLAB (Bode_bug_matlab.jpg) and from octave
(Bode_bug_octave.jpg).

As one can see, the Octave returns a frequency response with high-order (with
noise) and MATLAB returns a filtered one (without noise).

On my interpretation, MATLAB is cancelling some pole and zeros inside a
unknown precision range. However, I am not sure if the octave result is
correct or it is just plotting something due to numeric errors.

All the files to reproduce the error are attached.

Thanks.

         

 





All files are attached.   







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File Attachments:


-------------------------------------------------------
Date: seg 21 nov 2022 13:57:52  Name: Bode_bug_matlab.jpg  Size: 20KiB   By:
luiz

<http://savannah.gnu.org/bugs/download.php?file_id=53981>
-------------------------------------------------------
Date: seg 21 nov 2022 13:57:52  Name: TF.mat  Size: 648B   By: luiz

<http://savannah.gnu.org/bugs/download.php?file_id=53982>
-------------------------------------------------------
Date: seg 21 nov 2022 13:57:52  Name: Bode_bug_octave.jpg  Size: 59KiB   By:
luiz

<http://savannah.gnu.org/bugs/download.php?file_id=53983>
-------------------------------------------------------
Date: seg 21 nov 2022 13:57:52  Name: bode_bug.m  Size: 102B   By: luiz

<http://savannah.gnu.org/bugs/download.php?file_id=53984>

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