[Octave-bug-tracker] [bug #43506] fir1 returns completely wrong results

[John]

URL:
  <http://savannah.gnu.org/bugs/?43506>

                 Summary: fir1 returns completely wrong results
                 Project: GNU Octave
            Submitted by: jcoppens
            Submitted on: Fri 31 Oct 2014 03:14:30 AM GMT
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: John
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.1
        Operating System: GNU/Linux

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Details:

Somewhat surprised when I submitted a simple bandpass filter to the fir1
function and got wrong results (according docs the fir1 should return a
bandpass by default, which it did not, but even when specifying the filter
type, the result was the same, i.e. wrong).

I then looked up the docs for Matlab docs and submitted the example to
Octave:

octave:2> b = fir1(48,[0.35 0.65]);
octave:3> freqz(b,1,512)

The result from Matlab is in the first attachment, the result from Octave in
the second. Maybe I'm doing something wrong here?
It seems the upper limit is more or less correct, but the lower limit is
always at 0. Adding ", 'bandpass'" makes no difference.

Octave is version 3.8.1.



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File Attachments:


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Date: Fri 31 Oct 2014 03:14:30 AM GMT  Name: Screenshot - 10302014 - 09:55:41
PM.png  Size: 36kB   By: jcoppens

<http://savannah.gnu.org/bugs/download.php?file_id=32346>
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Date: Fri 31 Oct 2014 03:14:30 AM GMT  Name: Screenshot - 10302014 - 09:56:13
PM.png  Size: 16kB   By: jcoppens

<http://savannah.gnu.org/bugs/download.php?file_id=32347>

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