From help-request at octave dot org Wed Jan 12 09:05:15 2005
Subject: freqz inconsistency ?
From: "Pascal A. Dupuis" <Pascal dot Dupuis at esat dot kuleuven dot ac dot be>
To: help at octave dot org
Date: Wed, 12 Jan 2005 08:56:17 -0600

Hello,

I'm trying to understand some issues with invfreqz, and found some
inconsistency in freqz:

pdi = 0.97;
[Zz1, Wz1]=freqz((1-pdi), [1 -pdi], 128);
[Zz2, Wz2]=freqz((1-pdi), [1 -pdi], Wz1);

norm(Wz1-Wz2)
ans = 0

norm(Zz1-Zz2)
ans = 0.35010

as both frequency responses are evaluated at the same points, they
should give the same result, shouldn't they ?

I tried cheating a bit with 
[Zz2, Wz2]=freqz((1-pdi), [1 -pdi], const*Wz1);
but couldn't find a constant such that both frequency responses are
the same. Any idea ?

TIA

Pascal Dupuis

-- 
Dr. ir. Pascal Dupuis
K. U. Leuven, ESAT/ELECTA (formerly ELEN):  http://www.esat.kuleuven.ac.be/
Kasteelpark Arenberg, 10; B-3001 Leuven-Heverlee, Belgium
Tel. +32-16-32 10 21 -- Fax +32-16-32 19 85



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