bugGNU Octave - Bugs: bug #44008, freqz nuance

 
 

bug #44008: freqz nuance

Submitted by:  None
Submitted on:  Thu 15 Jan 2015 12:58:59 AM UTC  
 
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Invalid Assigned to:  None
Originator Name:  Bill McEachen Originator Email:  -email is unavailable-
Open/Closed:  Closed Release:  3.8.2
Operating System:  Microsoft Windows

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Fri 16 Jan 2015 03:14:58 AM UTC, comment #3: 

No bother, please do report any future problems that you think might be bugs in Octave. Closing as invalid.

Mike Miller <mtmiller>
Project Administrator
Fri 16 Jan 2015 01:39:34 AM UTC, comment #2: 

well, I've convinced myself all is ok, sorry for the bother, I'll try to check more thoroughly next time ....
BMcE

Anonymous
Thu 15 Jan 2015 02:12:16 AM UTC, comment #1: 

Thanks for your bug report. I believe you are simply passing the wrong input to the freqz function. Please note that the object returned by the control package system functions is a cell array of vectors. To get the numerator and denominator as ordinary row vectors, use Hz.num{1} and Hz.den{1}.

And I don't know what you saw to suggest zero-padding the numerator, or what bug report you referred to in the attached file (can you provide a link?). But try updating your script to use the following call to freqz instead:

[fr, w] = freqz (Hz.num{1}*k, Hz.den{1}, 20);

Does this produce what you expect? Do you expect to be able to get this result in a different way that is not working?

Mike Miller <mtmiller>
Project Administrator
Thu 15 Jan 2015 12:58:59 AM UTC, original submission:  

hopefully I've got it right, but reporting just in case.
I entered an analog tf, used c2d to get discrete version.
The returned Hz had numerator 7 terms, denominator 8.
My sampling freq was 40 rad/s, and I wanted the discrete freq response in 20 increments over 0-Pi
I thought I should 0 pad...when I did this and went to use freqz, I get
octave:84> [fr,w]=freqz(numz,denz,20);
error: freqz: A(I): index out of bounds; value 20 out of bound 2

bode works fine ...the issue may be handoff between the control and the signal package (?)

the commands I used are attached ...

Anonymous

 

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Attached Files
file #32827:  bug_details.txt added by None (626B - text/plain - I can provide anything else you need)

 

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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-01-16 mtmiller StatusNeed Info => Invalid
        Open/ClosedOpen => Closed
    2015-01-15 mtmiller Item GroupOther => Incorrect Result
        StatusNone => Need Info
    2015-01-15 None Attached File- => Added bug_details.txt, #32827

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