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[Octave-bug-tracker] [bug #63636] Cheby1 - imaginary residual in gain va
From: |
anonymous |
Subject: |
[Octave-bug-tracker] [bug #63636] Cheby1 - imaginary residual in gain variable errors zp2tf |
Date: |
Mon, 9 Jan 2023 16:04:37 -0500 (EST) |
URL:
<https://savannah.gnu.org/bugs/?63636>
Summary: Cheby1 - imaginary residual in gain variable errors
zp2tf
Project: GNU Octave
Submitter: None
Submitted: Mon 09 Jan 2023 09:04:35 PM UTC
Category: Octave Forge Package
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Unexpected Error or Warning
Status: None
Assigned to: None
Originator Name:
Originator Email: gregory.white@ni.com
Open/Closed: Open
Release: 7.1.0
Discussion Lock: Any
Operating System: Microsoft Windows
Fixed Release: None
Planned Release: None
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Follow-up Comments:
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Date: Mon 09 Jan 2023 09:04:35 PM UTC By: Anonymous
This is a simple problem, so I embedded the test file cheby1_gain_error.m:
function cheby1_gain_error
% cheby1_gain_error - shows complex residual in cheby1 gain causes error in
zp2tf.
n = 5
rp = 10*log10(2)
[z,p,k] = cheb1ap(n,rp)
[num_lp, den_lp] = zp2tf(z, p, k)
% >> which cheby1
% 'cheby1' is a function from the file
C:\engineer\Octave-7.1.0\mingw64\share\octave\packages\signal-1.4.1\cheby1.m
% Line 115 is:
% gain = prod (-pole);
% Because of the method of computing "prod()", an imaginary residual is a
% possible result for the real axis zero (n is odd).
% While careful construction of the roots and then the computation of gain
% with those roots can avoid this, the brute force of enforcing real() upon
% prod() is likely a sufficient solution. Use
% gain = real (prod (-pole));
% instead for line 115.
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File Attachments:
-------------------------------------------------------
Date: Mon 09 Jan 2023 09:04:35 PM UTC Name: cheby1_gain_error.m Size: 761B
By: None
<http://savannah.gnu.org/bugs/download.php?file_id=54204>
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- [Octave-bug-tracker] [bug #63636] Cheby1 - imaginary residual in gain variable errors zp2tf,
anonymous <=