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[Octave-bug-tracker] [bug #51936] zp2sos wrong results for single zero
From: |
fietew |
Subject: |
[Octave-bug-tracker] [bug #51936] zp2sos wrong results for single zero |
Date: |
Mon, 4 Sep 2017 12:30:22 -0400 (EDT) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:54.0) Gecko/20100101 Firefox/54.0 |
URL:
<http://savannah.gnu.org/bugs/?51936>
Summary: zp2sos wrong results for single zero
Project: GNU Octave
Submitted by: fietew
Submitted on: Mon 04 Sep 2017 04:30:20 PM UTC
Category: Octave Forge Package
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: 4.0.0
Operating System: GNU/Linux
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Details:
Try:
zp2sos([1],[-1; 1], 1)
zp2sos([1; -1],[-1; 1], 1)
zp2sos([1; 0],[-1; 1], 1)
The input describes the following Systems:
1st Line: H(z) = (z-1)/((z-1)*(z+1)) = (z^(-1) - z^(-2))/(1-(z^-2))
2nd Line: H(z) = ((z-1)*(z+1))/((z-1)*(z+1)) = (1-z^(-2))/(1-z^(-2))
3rd Line: H(z) = ((z-1)*z)/((z-1)*(z+1)) = (1 - z^(-1))/(1-z^(-2))
Output:
ans =
1 -1 0 1 0 -1
ans =
1 0 -1 1 0 -1
ans =
1 -1 0 1 0 -1
The third output is equal to the first one, which should not be the case,
since the systems are not the same. The documentation
(https://octave.sourceforge.io/signal/function/zp2sos.html) says "The b0 entry
must be nonzero for each section.", which explains the behavior, but does not
preserve the properties of the first system.
_______________________________________________________
Reply to this item at:
<http://savannah.gnu.org/bugs/?51936>
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