[Octave-bug-tracker] [bug #36521] buttord() over designs

[Luke]

URL:
  <http://savannah.gnu.org/bugs/?36521>

                 Summary: buttord() over designs
                 Project: GNU Octave
            Submitted by: ltclifton
            Submitted on: Tue 22 May 2012 07:35:35 AM GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.1
        Operating System: Any

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Details:

The buttord() function in the signal processing library over designs band pass
filters. This seems to be a known issue as an error is printed at run-time.
However I could not find a corresponding bug report. I have confirmed that it
does over-design by comparing the output to Matlabs equivalent function.

The following example demonstrates

[n, Wn] = buttord([0.16 0.24], [0.12 0.32], 3, 12)

Octave reports that a 6th order filter is required.

Matlab report (correctly) that a 4th order filter is required.

While Octave's solution satisfies the requirements, it is misleading, and
buggy behavior to report this solution.




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